SL-14286 fixed crash when closing viewer while file picker is open

indra/newview/llappdelegate-objc.mm

@@ -134,6 +134,7 @@
 		// called again. Since it returned false, do not yet cancel
 		// frameTimer.
 		handleQuit();
+		[[NSApplication sharedApplication] stopModal];
 		return NSTerminateCancel;
 	} else {
 		// pumpMainLoop() returned true: it's done. Okay, done with frameTimer.

indra/newview/llfloatermodelpreview.cpp

@@ -103,6 +103,11 @@ LLMeshFilePicker::LLMeshFilePicker(LLModelPreview* mp, S32 lod)
 
 void LLMeshFilePicker::notify(const std::vector<std::string>& filenames)
 {
+	if(LLAppViewer::instance()->quitRequested())
+	{
+		return;
+	}
+	
 	if (filenames.size() > 0)
 	{
 		mMP->loadModel(filenames[0], mLOD);