UI: Don't trigger a settings update when list is empty

To avoid recursive call

(cherry picked from commit 4871fd301afb9806e158e6b0ebad3ba74868602d)

UI/properties-view.cpp

@@ -647,7 +647,7 @@ QWidget *OBSPropertiesView::AddList(obs_property_t *prop, bool &warning)
 	children.emplace_back(info);
 
 	/* trigger a settings update if the index was not found */
-	if (idx == -1)
+	if (count && idx == -1)
 		info->ControlChanged();
 
 	return combo;