Clang backend crashes on opening stl_deque.h

In the attached test project, when following to the definition of `std::deque`, clangbackend starts to repeatedly crash.

1. Open the project and run CMake.
2. Point the cursor to the `std::deque` type of `m_foos` and follow to the type definition.
3. QtCreator opens stl_deque.h:849 and clangbackend starts crashing repeatedly with the following message:

2020-07-23T15:27:53 Clang Code Model: Error: The clangbackend process has finished unexpectedly and was restarted.

This is happening on Kubuntu 20.04 with its stock gcc 9.3 (the stl_deque.h file is from libstdc++ used with that compiler).