Fix crash when completely removing a file type from pro file.

The wrong category folder (like Sources/Headers) would be deleted from
the project tree, because all category folders had the same path.
The nodes' path is used everywhere for performance optimization.

src/plugins/qt4projectmanager/qt4nodes.cpp

@@ -404,7 +404,7 @@ void Qt4PriFileNode::update(ProFile *includeFile, ProFileReader *reader)
             InternalNode *subfolder = new InternalNode;
             subfolder->type = type;
             subfolder->icon = fileTypeIcons.at(i);
-            subfolder->fullName = m_projectDir;
+            subfolder->fullName = m_projectDir + '#' + fileTypeNames.at(i);
             contents.subnodes.insert(fileTypeNames.at(i), subfolder);
             // create the hierarchy with subdirectories
             subfolder->create(m_projectDir, newFilePaths, type);