Fixed UI API called on a background thread.

@@ -4736,14 +4736,18 @@ static NSOperationQueue *sharedQueue = nil;
 + (void)showNetworkActivityIndicator
 {
 #if TARGET_OS_IPHONE
-	[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
+    dispatch_async(dispatch_get_main_queue(), ^{
+        [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
+    });
 #endif
 }
 
 + (void)hideNetworkActivityIndicator
 {
 #if TARGET_OS_IPHONE
-	[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];	
+    dispatch_async(dispatch_get_main_queue(), ^{
+        [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
+    });
 #endif
 }