Fixes: Crash in the flat model on certain changes to the pro file.

Task:     240180
Details:  Hopefully fixes a few crashes people have reported.

src/plugins/projectexplorer/projectmodels.cpp

@@ -1144,7 +1144,7 @@ void FlatModel::foldersAboutToBeRemoved(FolderNode *parentFolder, const QList<Fo
     FolderNode *folderNode = visibleFolderNode(parentFolder);
     QList<Node *> newNodeList = childNodes(folderNode, blackList);
 
-    removed(parentFolder, newNodeList);
+    removed(folderNode, newNodeList);
     removeFromCache(staleFolders);
 }