title: Firebase database getInstance crashes app
body: <p>When running the sample after creating google-service.json, the app crashes when trying to get database reference in SignInActivity</p>
  
  <pre><code>mDatabase = FirebaseDatabase.getInstance().getReference();
  </code></pre>
  
  <p>Crash log</p>
  
  <pre><code>05-21 09:27:27.644 488-488/com.google.firebase.quickstart.database D/AndroidRuntime: Shutting down VM
  05-21 09:27:27.644 488-488/com.google.firebase.quickstart.database E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                       Process: com.google.firebase.quickstart.database, PID: 488
                                                                                       java.lang.RuntimeException: Unable to start activity ComponentInfo{com.google.firebase.quickstart.database/com.google.firebase.quickstart.database.SignInActivity}: com.google.firebase.database.DatabaseException: Failed to get 
  
  FirebaseDatabase instance: FirebaseApp object has no DatabaseURL in its FirebaseOptions object.
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
       at android.app.ActivityThread.access$800(ActivityThread.java:151)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
       at android.os.Handler.dispatchMessage(Handler.java:102)
       at android.os.Looper.loop(Looper.java:135)
       at android.app.ActivityThread.main(ActivityThread.java:5254)
       at java.lang.reflect.Method.invoke(Native Method)
       at java.lang.reflect.Method.invoke(Method.java:372)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
    Caused by: com.google.firebase.database.DatabaseException: Failed to get FirebaseDatabase instance: FirebaseApp object has no DatabaseURL in its FirebaseOptions object.
       at com.google.firebase.database.FirebaseDatabase.getInstance(Unknown Source)
       at com.google.firebase.database.FirebaseDatabase.getInstance(Unknown Source)
       at com.google.firebase.quickstart.database.SignInActivity.onCreate(SignInActivity.java:39)
       at android.app.Activity.performCreate(Activity.java:5990)
       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) 
       at android.app.ActivityThread.access$800(ActivityThread.java:151) 
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) 
       at android.os.Handler.dispatchMessage(Handler.java:102) 
       at android.os.Looper.loop(Looper.java:135) 
       at android.app.ActivityThread.main(ActivityThread.java:5254) 
       at java.lang.reflect.Method.invoke(Native Method) 
       at java.lang.reflect.Method.invoke(Method.java:372) 
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 
  </code></pre>
  
  <p>How to fix this issue ?</p>