I\'ve restarted Android Studio (version 1.1.0 built on 18 Feb) & now Crashlytics can\'t be initialized with this error:
NullPointerEx
If you can't solve this issue, I found a way that worked (Android Studio 1.1 on OSX).
Uninstall AS.
Delete the following (~ is home directory of user who runs AS):
~/.android*
~/.Android*
~/Library/Preferences/AndroidStudio*
~/Library/Preferences/com.google.android*
~/Library/Caches/Android*
~/Library/Android*
~/Library/Caches/com.crashlytics*
~/Library/Application Support/AndroidStudio*
~/Library//Saved Application State/com.google.android.studio.savedState
Then re-install Android Studio and the Fabric plugin, and it should work now.
I don't know if all the above deletes are necessary, but I could not narrow it down any further, and deleting all the above after uninstalling, then re-installing, worked for me.