fix uninitialized variable in block capture

Author: morganchen12

FirebaseDatabaseUI/FirebaseIndexArray.h

@@ -71,7 +71,7 @@ didFailLoadWithError:(NSError *)error;
 - (void)array:(FirebaseIndexArray *)array didAddReference:(FIRDatabaseReference *)ref atIndex:(NSUInteger)index;
 
 /**
- * Delegate method which is called whenever an object is chinged in a
+ * Delegate method which is called whenever an object is changed in a
  * FirebaseArray. On a
  * FirebaseArray synchronized to a Firebase reference, this corresponds to an
  * [FIRDataEventTypeChildChanged](https://www.firebase.com/docs/ios/guide/retrieving-data.html#section-event-types)

FirebaseDatabaseUI/FirebaseIndexArray.m

@@ -131,9 +131,10 @@ - (void)array:(FirebaseArray *)array
   NSParameterAssert([object.key isKindOfClass:[NSString class]]);
   id<FIRDataObservable> query = [self.data child:object.key];
   FirebaseQueryObserver *obs = [FirebaseQueryObserver observerForQuery:query
-                                                            completion:^(FIRDataSnapshot *snap,
+                                                            completion:^(FirebaseQueryObserver *observer,
+                                                                         FIRDataSnapshot *snap,
                                                                          NSError *error) {
-    [self observer:obs didFinishLoadWithSnap:snap error:error];
+    [self observer:observer didFinishLoadWithSnap:snap error:error];
   }];
   [self.observers insertObject:obs atIndex:index];
 
@@ -168,9 +169,10 @@ - (void)array:(FirebaseArray *)array
   // Add new observer
   id<FIRDataObservable> query = [self.data child:object.key];
   FirebaseQueryObserver *obs = [FirebaseQueryObserver observerForQuery:query
-                                                            completion:^(FIRDataSnapshot *snap,
+                                                            completion:^(FirebaseQueryObserver *observer,
+                                                                         FIRDataSnapshot *snap,
                                                                          NSError *error) {
-    [self observer:obs didFinishLoadWithSnap:snap error:error];
+    [self observer:observer didFinishLoadWithSnap:snap error:error];
   }];
   [self.observers replaceObjectAtIndex:index withObject:obs];
 

FirebaseDatabaseUI/FirebaseQueryObserver.h

@@ -38,7 +38,8 @@ NS_ASSUME_NONNULL_BEGIN
  * Creates a query observer and immediately starts observing the query.
  */
 + (FirebaseQueryObserver *)observerForQuery:(id<FIRDataObservable>)query
-                                 completion:(void (^_Nullable)(FIRDataSnapshot *_Nullable,
+                                 completion:(void (^_Nullable)(FirebaseQueryObserver *obs,
+                                                               FIRDataSnapshot *_Nullable,
                                                                NSError *_Nullable))completion;
 
 /**

FirebaseDatabaseUI/FirebaseQueryObserver.m

@@ -44,16 +44,18 @@ - (instancetype)initWithQuery:(id<FIRDataObservable>)query {
 }
 
 + (FirebaseQueryObserver *)observerForQuery:(id<FIRDataObservable>)query
-                                 completion:(void (^)(FIRDataSnapshot *snap, NSError *error))completion {
+                                 completion:(void (^)(FirebaseQueryObserver *obs,
+                                                      FIRDataSnapshot *snap,
+                                                      NSError *error))completion {
   FirebaseQueryObserver *obs = [[FirebaseQueryObserver alloc] initWithQuery:query];
 
   void (^observerBlock)(FIRDataSnapshot *, NSString *) = ^(FIRDataSnapshot *snap,
                                                            NSString *previous) {
     obs.contents = snap;
-    completion(snap, nil);
+    completion(obs, snap, nil);
   };
   void (^cancelBlock)(NSError *) = ^(NSError *error) {
-    completion(nil, error);
+    completion(obs, nil, error);
   };
 
   [obs observeEventType:FIRDataEventTypeChildAdded