title: app crashes when 'create new account' is clicked
body: <p>App crashes whenever I click 'create new account' button. The error in Logcat states that I need to call FirebaseApp.initialize(this); which I've done but still the same error occurs. Here is my RegisterActivity.</p>
  
  <pre><code>private FirebaseAuth mAuth;
  private ProgressDialog loadingbar;
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_register);
  
      FirebaseApp.initializeApp(this);
      mAuth = FirebaseAuth.getInstance();
  </code></pre>
  
  <p>And my Logcat is below.</p>
  
  <pre><code> Process: com.example.whatsappclone, PID: 9246
  java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.whatsappclone/com.example.whatsappclone.RegisterActivity}: java.lang.IllegalStateException: Default FirebaseApp is not initialized in this process com.example.whatsappclone. Make sure to call FirebaseApp.initializeApp(Context) first.
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
      at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
      at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
      at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
      at android.os.Handler.dispatchMessage(Handler.java:106)
      at android.os.Looper.loop(Looper.java:193)
      at android.app.ActivityThread.main(ActivityThread.java:6669)
      at java.lang.reflect.Method.invoke(Native Method)
      at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
   Caused by: java.lang.IllegalStateException: Default FirebaseApp is not initialized in this process com.example.whatsappclone. Make sure to call FirebaseApp.initializeApp(Context) first.
      at com.google.firebase.FirebaseApp.getInstance(com.google.firebase:firebase-common@@16.0.2:240)
      at com.google.firebase.auth.FirebaseAuth.getInstance(Unknown Source:1)
      at com.example.whatsappclone.RegisterActivity.onCreate(RegisterActivity.java:36)
      at android.app.Activity.performCreate(Activity.java:7136)
      at android.app.Activity.performCreate(Activity.java:7127)
  </code></pre>