Fixing a bug in both debug tools (image scaling, tappable area) in which I don't check that the overlay exists before creating it.

Author: hannahmbanana

AsyncDisplayKit/ASControlNode.mm

@@ -262,7 +262,7 @@ - (void)addTarget:(id)target action:(SEL)action forControlEvents:(ASControlNodeE
     _controlEventDispatchTable = [[NSMutableDictionary alloc] initWithCapacity:kASControlNodeEventDispatchTableInitialCapacity]; // enough to handle common types without re-hashing the dictionary when adding entries.
 
     // only show tap-able areas for views with 1 or more addTarget:action: pairs
-    if ([ASControlNode enableHitTestDebug]) {
+    if ([ASControlNode enableHitTestDebug] && _debugHighlightOverlay == nil) {
       ASPerformBlockOnMainThread(^{
         // add a highlight overlay node with area of ASControlNode + UIEdgeInsets
         self.clipsToBounds = NO;

AsyncDisplayKit/ASImageNode.mm

@@ -140,7 +140,7 @@ - (void)setImage:(UIImage *)image
     if (image) {
       [self setNeedsDisplay];
 
-      if ([ASImageNode shouldShowImageScalingOverlay]) {
+      if ([ASImageNode shouldShowImageScalingOverlay] && _debugLabelNode == nil) {
         ASPerformBlockOnMainThread(^{
           _debugLabelNode = [[ASTextNode alloc] init];
           _debugLabelNode.layerBacked = YES;