fixes issue affecting list of listeners (parse-community#1182)

Author: flovilmart

Parse/Internal/PFReachability.m

@@ -135,7 +135,7 @@ - (void)removeListener:(id<PFReachabilityListener>)listener {
         @strongify(listener);
         [_listenersArray filterUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(id evaluatedObject, NSDictionary *bindings) {
             id weakObject = [evaluatedObject weakObject];
-            return (weakObject == nil || weakObject == listener);
+            return !(weakObject == nil || weakObject == listener);
         }]];
     });
 }
@@ -156,7 +156,7 @@ - (void)_notifyAllListeners {
         }
 
         dispatch_barrier_async(_synchronizationQueue, ^{
-            [_listenersArray filterUsingPredicate:[NSPredicate predicateWithFormat:@"SELf.weakObject != nil"]];
+            [_listenersArray filterUsingPredicate:[NSPredicate predicateWithFormat:@"SELF.weakObject != nil"]];
         });
     });
 }