title: "Can't pass null for argument 'pathString' in child()" and other Proguard and Firebase issues
body: <p>I'm at wits end with Proguard and Firebase. Proguard seems to be causing issue after issue with the release version of <a href="https://github.com/langsmith/ChildChip" rel="nofollow">my Play Store app</a>. </p>
  
  <p>Here's what's is currently in my proguard-rules.pro file:</p>
  
  <pre><code>-keepattributes Signature
  
  -keepclassmembers class com.test.finalapp.models.** { *;}
  
  
  -keep class com.test.finalapp.viewholders.** { *; }
  
  -dontwarn android.support.v7.**
  -keep class android.support.v7.** { *; }
  -keep interface android.support.v7.** { *; }
  
  -keepattributes *Annotation*
  -keepclassmembers class ** {
      @org.greenrobot.eventbus.Subscribe &lt;methods&gt;;
  }
  -keep enum org.greenrobot.eventbus.ThreadMode { *; }
  
  -keepclassmembers class ** { public void onEvent*(**); }
  </code></pre>
  
  <p>I'm using a FirebaseUI RecyclerView adapter and that adapter's viewholder class is in the viewholders package name. So that's what that line in the proguard-rules.pro file is for. </p>
  
  <p>Side question: Does capitalization matter in the proguard-rules file?  Should viewholders be capitalized in "com.test.finalapp.viewholders" if my package is named "Viewholders"?</p>
  
  <p>ANYWAYS, here's the latest logcat error that I can't figure out:</p>
  
  <pre><code>09-16 16:16:46.899 882-882/? E/UncaughtException: java.lang.NullPointerException: Can't pass null for argument 'pathString' in child()
                                                        at com.google.firebase.database.g.a(Unknown Source)
                                                        at com.test.finalapp.Activities.PreMainActivities.c.a(Unknown Source)
                                                        at com.google.firebase.database.p.a(Unknown Source)
                                                        at com.google.android.gms.c.ha.a(Unknown Source)
                                                        at com.google.android.gms.c.iv.b(Unknown Source)
                                                        at com.google.android.gms.c.jb.run(Unknown Source)
                                                        at android.os.Handler.handleCallback(Handler.java:739)
                                                        at android.os.Handler.dispatchMessage(Handler.java:95)
                                                        at android.os.Looper.loop(Looper.java:152)
                                                        at android.app.ActivityThread.main(ActivityThread.java:5507)
                                                        at java.lang.reflect.Method.invoke(Native Method)
                                                        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
  09-16 16:16:47.102 882-882/? D/FirebaseCrashApiImpl: throwable java.lang.NullPointerException: Can't pass null for argument 'pathString' in child()
  
                                                       --------- beginning of crash
  09-16 16:16:47.141 882-882/? E/AndroidRuntime: FATAL EXCEPTION: main
                                                 Process: com.test.finalapp, PID: 882
                                                 java.lang.NullPointerException: Can't pass null for argument 'pathString' in child()
                                                     at com.google.firebase.database.g.a(Unknown Source)
                                                     at com.test.finalapp.Activities.PreMainActivities.c.a(Unknown Source)
                                                     at com.google.firebase.database.p.a(Unknown Source)
                                                     at com.google.android.gms.c.ha.a(Unknown Source)
                                                     at com.google.android.gms.c.iv.b(Unknown Source)
                                                     at com.google.android.gms.c.jb.run(Unknown Source)
                                                     at android.os.Handler.handleCallback(Handler.java:739)
                                                     at android.os.Handler.dispatchMessage(Handler.java:95)
                                                     at android.os.Looper.loop(Looper.java:152)
                                                     at android.app.ActivityThread.main(ActivityThread.java:5507)
                                                     at java.lang.reflect.Method.invoke(Native Method)
                                                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
  </code></pre>
  
  <p>I have no clue what ""Can't pass null for argument 'pathString' in child()" means, nor what to adjust to solve the problem. Thoughts? I couldn't find any solutions online before posting this question...</p>