title: IntelliJ: unable to import SBT project
body: <p>I've been using IntelliJ with SBT successfully for a while, but lately I've been unable to import SBT projects.</p>
  
  <p>I'll do the following:</p>
  
  <ul>
  <li><p>Create new project > Empty project</p></li>
  <li><p>Specify a new to-be-created folder</p></li>
  <li><p>Add > Import module in the dialog, or New > Module from existing sources from the menu</p></li>
  <li><p>Select the folder containing the SBT project</p></li>
  <li><p>Select SBT</p></li>
  <li><p>Finish</p></li>
  </ul>
  
  <p>The project does not show up anywhere in IntelliJ. The status line says "Unable to save settings". If I try to import the project once again I get "This project is already registered".</p>
  
  <p>Here is a snippet from <code>idea.log</code> that looks like it could be relevant:</p>
  
  <pre><code>Caused by: java.lang.Exception: Cannot get libraryTable component state
      at com.intellij.configurationStore.ComponentStoreImpl.save(ComponentStoreImpl.kt:166)
  ... 38 more
  Caused by: java.lang.NullPointerException
      at org.jetbrains.plugins.scala.project.ScalaLibraryProperties.getState(ScalaLibraryProperties.scala:30)
      at org.jetbrains.plugins.scala.project.ScalaLibraryProperties.getState(ScalaLibraryProperties.scala:14)
      at com.intellij.openapi.roots.impl.libraries.LibraryImpl.writeExternal(LibraryImpl.java:368)
      at com.intellij.openapi.roots.impl.libraries.LibraryTableBase$LibraryModel.writeExternal(LibraryTableBase.java:363)
      at com.intellij.openapi.roots.impl.libraries.LibraryTableBase.getState(LibraryTableBase.java:63)
      at com.intellij.openapi.roots.impl.libraries.LibraryTableBase.getState(LibraryTableBase.java:45)
      at com.intellij.configurationStore.ComponentStoreImpl.commitComponent(ComponentStoreImpl.kt:227)
      at com.intellij.configurationStore.ComponentStoreImpl.save(ComponentStoreImpl.kt:159)
  </code></pre>
  
  <p>IntelliJ 2017.2.3, Scala plugin 2017.2.6.</p>