Fix startAt, endAt, equalTo optional 2nd params on Android

[BlooJeans]

Fixes

E/unknown:React: Exception in native call java.lang.ArrayIndexOutOfBoundsException: length=2; index=2 at io.fullstack.firestack.FirestackDBReference.getDatabaseQueryAtPathAndModifiers(FirestackDatabase.java:235) at io.fullstack.firestack.FirestackDBReference.addChildEventListener(FirestackDatabase.java:90) at io.fullstack.firestack.FirestackDatabaseModule.on(FirestackDatabase.java:379) at java.lang.reflect.Method.invoke(Native Method) at com.facebook.react.bridge.BaseJavaModule$JavaMethod.invoke(BaseJavaModule.java:319) at com.facebook.react.cxxbridge.JavaModuleWrapper.invoke(JavaModuleWrapper.java:158) at com.facebook.react.bridge.queue.NativeRunnable.run(Native Method) at android.os.Handler.handleCallback(Handler.java:751) at android.os.Handler.dispatchMessage(Handler.java:95) at com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage(MessageQueueThreadHandler.java:31) at android.os.Looper.loop(Looper.java:154) at com.facebook.react.bridge.queue.MessageQueueThreadImpl$3.run(MessageQueueThreadImpl.java:196) at java.lang.Thread.run(Thread.java:761)