ProjectNodes: Enable nested nodes outside of the top level node

Enable adding nested nodes not a child of the top level node.

Change-Id: Ia6bb4ed6e3e6649a98151c88133ff5ec7197573d
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/projectexplorer/projectnodes.cpp

@@ -77,6 +77,7 @@ static FolderNode *recursiveFindOrCreateFolderNode(FolderNode *folder,
             directoryWithoutPrefix = directory.relativeChildPath(path);
         } else {
             isRelative = false;
+            path.clear();
             directoryWithoutPrefix = directory;
         }
     }