MAINT-6461 Added a null check

indra/llui/llview.cpp

@@ -588,6 +588,11 @@ void LLView::onVisibilityChange ( BOOL new_visibility )
 	BOOL log_visibility_change = LLViewerEventRecorder::instance().getLoggingStatus();
 	BOOST_FOREACH(LLView* viewp, mChildList)
 	{
+		if (!viewp)
+		{
+			continue;
+		}
+
 		// only views that are themselves visible will have their overall visibility affected by their ancestors
 		old_visibility=viewp->getVisible();