Fix deadlock when loadStore posts notifications to the main thread.

platform-darwin/Source/iOS/MPiOSAppDelegate.m

@@ -132,8 +132,10 @@ MP_LIBS_END
             [self updateConfigKey:note.object];
         } );
         PearlAddNotificationObserver( NSUserDefaultsDidChangeNotification, nil, nil, ^(id self, NSNotification *note) {
+            PearlMainQueueOperation( ^{
                 [[NSNotificationCenter defaultCenter] postNotificationName:MPCheckConfigNotification object:nil];
             } );
+        } );
     }
     @catch (id exception) {
         err( @"During Config Test: %@", exception );