dispatch_sync -> dispatch_async

UIKit+AFNetworking/UIActivityIndicatorView+AFNetworking.m

@@ -68,13 +68,13 @@
 #pragma mark -
 
 - (void)af_startAnimating {
-    dispatch_sync(dispatch_get_main_queue(), ^{
+    dispatch_async(dispatch_get_main_queue(), ^{
         [self startAnimating];
     });
 }
 
 - (void)af_stopAnimating {
-    dispatch_sync(dispatch_get_main_queue(), ^{
+    dispatch_async(dispatch_get_main_queue(), ^{
         [self stopAnimating];
     });
 }