SL-16234 FIXED Frame stall caused by unnecessary building the floater when exiting viewer

indra/llui/llfloater.h

@@ -346,6 +346,8 @@ public:
 	// handle refocusing.
 	static void		closeFrontmostFloater();
 
+    static bool     isQuitRequested() { return sQuitting; }
+
 //	LLNotification::Params contextualNotification(const std::string& name) 
 //	{ 
 //	    return LLNotification::Params(name).context(mNotificationContext); 

indra/newview/llfloaterimcontainer.cpp

@@ -723,7 +723,13 @@ void LLFloaterIMContainer::setMinimized(BOOL b)
 }
 
 void LLFloaterIMContainer::setVisible(BOOL visible)
-{	LLFloaterIMNearbyChat* nearby_chat;
+{
+    if (LLFloater::isQuitRequested())
+    {
+        return;
+    }
+
+    LLFloaterIMNearbyChat* nearby_chat;
 	if (visible)
 	{
 		// Make sure we have the Nearby Chat present when showing the conversation container