title: Error when uploading crashlytics mapping file when building signed Apk
body: <p>When building signed apk with proguard for Crashlytics</p>
  <p>I am getting below error</p>
  <pre><code>* What went wrong:
  Execution failed for task ':app:uploadCrashlyticsMappingFileProProdRelease'.
  &gt; Expected file collection to contain exactly one file, however, it contains no files.
  </code></pre>
  <p>Project level gradle</p>
  <pre><code>dependencies {
      classpath 'com.android.tools.build:gradle:3.6.3'
      classpath 'com.google.gms:google-services:4.3.3'
      classpath 'com.google.firebase:firebase-crashlytics-gradle:2.2.0'
  }
  </code></pre>
  <p>App Level gradle</p>
  <pre><code>apply plugin: 'com.google.firebase.crashlytics'
  
  dependencies {
      implementation 'com.google.firebase:firebase-crashlytics:17.1.0'
  }
  </code></pre>
  <p>Android Studio version 4.0.1</p>
  <p>Full stacktrace for the same</p>
  <p><code>Exception is: org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':app:uploadCrashlyticsMappingFileProProdRelease'. at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$3.accept(ExecuteActionsTaskExecuter.java:166) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$3.accept(ExecuteActionsTaskExecuter.java:163) at org.gradle.internal.Try$Failure.ifSuccessfulOrElse(Try.java:191) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:156) at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:62) at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:108) at org.gradle.api.internal.tasks.execution.ResolveBeforeExecutionOutputsTaskExecuter.execute(ResolveBeforeExecutionOutputsTaskExecuter.java:67) at org.gradle.api.internal.tasks.execution.ResolveAfterPreviousExecutionStateTaskExecuter.execute(ResolveAfterPreviousExecutionStateTaskExecuter.java:46) at org.gradle.api.internal.tasks.execution.CleanupStaleOutputsExecuter.execute(CleanupStaleOutputsExecuter.java:94) at org.gradle.api.internal.tasks.execution.FinalizePropertiesTaskExecuter.execute(FinalizePropertiesTaskExecuter.java:46) at org.gradle.api.internal.tasks.execution.ResolveTaskExecutionModeExecuter.execute(ResolveTaskExecutionModeExecuter.java:95) at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:57) at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:56) at org.gradle.api.internal.tasks.execution.CatchExceptionTaskExecuter.execute(CatchExceptionTaskExecuter.java:36) at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.executeTask(EventFiringTaskExecuter.java:77) at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.call(EventFiringTaskExecuter.java:55) at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.call(EventFiringTaskExecuter.java:52) at org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:416) at org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:406) at org.gradle.internal.operations.DefaultBuildOperationExecutor$1.execute(DefaultBuildOperationExecutor.java:165) at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:250) at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:158) at org.gradle.internal.operations.DefaultBuildOperationExecutor.call(DefaultBuildOperationExecutor.java:102) at org.gradle.internal.operations.DelegatingBuildOperationExecutor.call(DelegatingBuildOperationExecutor.java:36) at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter.execute(EventFiringTaskExecuter.java:52) at org.gradle.execution.plan.LocalTaskNodeExecutor.execute(LocalTaskNodeExecutor.java:43) at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$InvokeNodeExecutorsAction.execute(DefaultTaskExecutionGraph.java:355) at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$InvokeNodeExecutorsAction.execute(DefaultTaskExecutionGraph.java:343) at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$BuildOperationAwareExecutionAction.execute(DefaultTaskExecutionGraph.java:336) at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$BuildOperationAwareExecutionAction.execute(DefaultTaskExecutionGraph.java:322) at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker$1.execute(DefaultPlanExecutor.java:134) at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker$1.execute(DefaultPlanExecutor.java:129) at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.execute(DefaultPlanExecutor.java:202) at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.executeNextNode(DefaultPlanExecutor.java:193) at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.run(DefaultPlanExecutor.java:129) at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:64) at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:48) at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:56) Caused by: java.lang.IllegalStateException: Expected file collection to contain exactly one file, however, it contains no files. at org.gradle.api.internal.file.AbstractFileCollection.getSingleFile(AbstractFileCollection.java:64) at org.gradle.api.file.FileCollection$getSingleFile.call(Unknown Source) at com.google.firebase.crashlytics.buildtools.gradle.tasks.UploadMappingFileTask.uploadMappingFile(UploadMappingFileTask.groovy:60) at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:103) at org.gradle.api.internal.project.taskfactory.StandardTaskAction.doExecute(StandardTaskAction.java:49) at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:42) at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:28) at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:717) at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:684) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$5.run(ExecuteActionsTaskExecuter.java:476) at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:402) at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:394) at org.gradle.internal.operations.DefaultBuildOperationExecutor$1.execute(DefaultBuildOperationExecutor.java:165) at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:250) at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:158) at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:92) at org.gradle.internal.operations.DelegatingBuildOperationExecutor.run(DelegatingBuildOperationExecutor.java:31) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:461) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:444) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.access$200(ExecuteActionsTaskExecuter.java:93) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$TaskExecution.execute(ExecuteActionsTaskExecuter.java:237) at org.gradle.internal.execution.steps.ExecuteStep.lambda$execute$1(ExecuteStep.java:33) at org.gradle.internal.execution.steps.ExecuteStep.execute(ExecuteStep.java:33) at org.gradle.internal.execution.steps.ExecuteStep.execute(ExecuteStep.java:26) at org.gradle.internal.execution.steps.CleanupOutputsStep.execute(CleanupOutputsStep.java:58) at org.gradle.internal.execution.steps.CleanupOutputsStep.execute(CleanupOutputsStep.java:35) at org.gradle.internal.execution.steps.ResolveInputChangesStep.execute(ResolveInputChangesStep.java:48) at org.gradle.internal.execution.steps.ResolveInputChangesStep.execute(ResolveInputChangesStep.java:33) at org.gradle.internal.execution.steps.CancelExecutionStep.execute(CancelExecutionStep.java:39) at org.gradle.internal.execution.steps.TimeoutStep.executeWithoutTimeout(TimeoutStep.java:73) at org.gradle.internal.execution.steps.TimeoutStep.execute(TimeoutStep.java:54) at org.gradle.internal.execution.steps.CatchExceptionStep.execute(CatchExceptionStep.java:35) at org.gradle.internal.execution.steps.CreateOutputsStep.execute(CreateOutputsStep.java:51) at org.gradle.internal.execution.steps.SnapshotOutputsStep.execute(SnapshotOutputsStep.java:45) at org.gradle.internal.execution.steps.SnapshotOutputsStep.execute(SnapshotOutputsStep.java:31) at org.gradle.internal.execution.steps.CacheStep.executeWithoutCache(CacheStep.java:208) at org.gradle.internal.execution.steps.CacheStep.execute(CacheStep.java:70) at org.gradle.internal.execution.steps.CacheStep.execute(CacheStep.java:45) at org.gradle.internal.execution.steps.BroadcastChangingOutputsStep.execute(BroadcastChangingOutputsStep.java:49) at org.gradle.internal.execution.steps.StoreSnapshotsStep.execute(StoreSnapshotsStep.java:43) at org.gradle.internal.execution.steps.StoreSnapshotsStep.execute(StoreSnapshotsStep.java:32) at org.gradle.internal.execution.steps.RecordOutputsStep.execute(RecordOutputsStep.java:38) at org.gradle.internal.execution.steps.RecordOutputsStep.execute(RecordOutputsStep.java:24) at org.gradle.internal.execution.steps.SkipUpToDateStep.executeBecause(SkipUpToDateStep.java:96) at org.gradle.internal.execution.steps.SkipUpToDateStep.lambda$execute$0(SkipUpToDateStep.java:89) at org.gradle.internal.execution.steps.SkipUpToDateStep.execute(SkipUpToDateStep.java:54) at org.gradle.internal.execution.steps.SkipUpToDateStep.execute(SkipUpToDateStep.java:38) at org.gradle.internal.execution.steps.ResolveChangesStep.execute(ResolveChangesStep.java:76) at org.gradle.internal.execution.steps.ResolveChangesStep.execute(ResolveChangesStep.java:37) at org.gradle.internal.execution.steps.legacy.MarkSnapshottingInputsFinishedStep.execute(MarkSnapshottingInputsFinishedStep.java:36) at org.gradle.internal.execution.steps.legacy.MarkSnapshottingInputsFinishedStep.execute(MarkSnapshottingInputsFinishedStep.java:26) at org.gradle.internal.execution.steps.ResolveCachingStateStep.execute(ResolveCachingStateStep.java:90) at org.gradle.internal.execution.steps.ResolveCachingStateStep.execute(ResolveCachingStateStep.java:48) at org.gradle.internal.execution.steps.CaptureStateBeforeExecutionStep.execute(CaptureStateBeforeExecutionStep.java:69) at org.gradle.internal.execution.steps.CaptureStateBeforeExecutionStep.execute(CaptureStateBeforeExecutionStep.java:47) at org.gradle.internal.execution.impl.DefaultWorkExecutor.execute(DefaultWorkExecutor.java:33) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:140) ... 34 more</code></p>