Fix crash presenting the loading frame while old one is still dismissing

Limelight/ViewControllers/LoadingFrameViewController.m

@@ -30,18 +30,46 @@
 
 - (void)showLoadingFrame:(void (^)(void))completion {
     if (!presented) {
+        Log(LOG_I, @"Loading frame presenting start");
         presented = YES;
-        [[self activeViewController] presentViewController:self animated:NO completion:completion];
+        [[self activeViewController] presentViewController:self animated:NO completion:^{
+            Log(LOG_I, @"Loading frame presenting complete");
+            if (completion) {
+                completion();
+            }
+        }];
     }
     else if (completion) {
+        Log(LOG_E, @"Loading frame already shown!");
         completion();
     }
 }
 
 - (void)dismissLoadingFrame:(void (^)(void))completion {
     if (presented) {
-        presented = NO;
+        Log(LOG_I, @"Loading frame hiding start");
-        [self dismissViewControllerAnimated:NO completion:completion];
+        [self dismissViewControllerAnimated:NO completion:^{
+            Log(LOG_I, @"Loading frame hiding complete");
+            
+            // Since presented is set to NO here rather than
+            // immediately in dismissLoadingFrame, we may
+            // falsely avoid displaying the loading frame if
+            // a dismiss is in progress while attempting to show
+            // the frame. That's preferable to crashing due to
+            // displaying the same VC twice though.
+            //
+            // This scenario can happen if the app is suspended
+            // while the dismiss is in progress then on resume
+            // it attempts to display it again before the dismiss
+            // completes. It can be reproduced by rapidly pressing
+            // Home and switching back to Moonlight while in the app grid.
+            // It reproduces more easily if the VC transitions are animated.
+            self->presented = NO;
+            
+            if (completion) {
+                completion();
+            }
+        }];
     }
     else if (completion) {
         completion();