Steps to reproduce:

• have clangd enabled, open a project (used QC here)
• open a file containing a license header (qmakeprojectmanagerplugin.cpp)
• have text cursor at the beginning of the file before the license header
• start typing something that is part of the file (m_run)
• wait for the completion proposal to appear
• use backspace to remove the inserted characters
• when removing the last char QC crashes

Expected result:

• completion proposal just vanishes without crashing QC

Looks like some mutex fail.. see attached backtrace (thread 15)