Merge branch 'master' of github.com:fullstackreact/react-native-firestack

* 'master' of github.com:fullstackreact/react-native-firestack:
  Fix Default app has already been configured
  Fix enablePersistence should be called before any access to FIRDatabase

Author: auser

ios/Firestack/Firestack.m

@@ -239,7 +239,9 @@ - (FIRApp *) firebaseApp
 
             // if (!self.configured) {
 
-            [FIRApp configureWithOptions:finalOptions];
+            if ([FIRApp defaultApp] == NULL) {
+                [FIRApp configureWithOptions:finalOptions];
+            }            
             [Firestack initializeFirestack:self];
             callback(@[[NSNull null], props]);
         }

ios/Firestack/FirestackDatabase.m

@@ -240,7 +240,11 @@ @implementation FirestackDatabase
 RCT_EXPORT_METHOD(enablePersistence:(BOOL) enable
   callback:(RCTResponseSenderBlock) callback)
 {
-  [FIRDatabase database].persistenceEnabled = enable;
+    
+  BOOL isEnabled = [FIRDatabase database].persistenceEnabled;
+  if ( isEnabled != enable) {
+    [FIRDatabase database].persistenceEnabled = enable;
+  }
   callback(@[[NSNull null], @{
     @"result": @"success"
   }]);