VWR-23444 FIXED Double clicking x on UI hint crashes Skylight Viewer

indra/newview/llhints.cpp

@@ -109,7 +109,14 @@ class LLHintPopup : public LLPanel
 
 	/*virtual*/ BOOL postBuild();
 
-	void onClickClose() { hide(); LLNotifications::instance().cancel(mNotification); }
+	void onClickClose() 
+	{ 
+		if (!mHidden) 
+		{
+			hide(); 
+			LLNotifications::instance().cancel(mNotification);
+		}
+	}
 	void draw();
 	void hide() { if(!mHidden) {mHidden = true; mFadeTimer.reset();} }