Fix NPE if status message is null in SignInDelegate

[SUPERCILEX]

The easy solution is to add a descriptive string in front of the getStatusMessage call and just let Java concat the two strings for us, thus guaranteeing that the end result won't be null. The other solution would be to add a null check and log a different message, though I'm not sure what we would say.

The crash:

Exception java.lang.NullPointerException: println needs a message

android.util.Log.println_native_inner (Log.java)
android.util.Log.println_native (Log.java:290)
android.util.Log.e (Log.java:416)
com.firebase.ui.auth.util.signincontainer.SignInDelegate.onResult (SignInDelegate.java:161)
com.firebase.ui.auth.util.signincontainer.SignInDelegate.onResult (SignInDelegate.java:59)
com.google.android.gms.internal.zzaaf$zza.handleMessage (zzaaf.java)
android.os.Handler.dispatchMessage (Handler.java:102)
android.os.Looper.loop (Looper.java:136)
android.app.ActivityThread.main (ActivityThread.java:5102)
java.lang.reflect.Method.invokeNative (Method.java)
java.lang.reflect.Method.invoke (Method.java:515)
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run (ZygoteInit.java:785)
com.android.internal.os.ZygoteInit.main (ZygoteInit.java:601)
dalvik.system.NativeStart.main (NativeStart.java)

[samtstern]

Wow, how have I been doing Android this long and never knew you couldn't log null? LGTM.