QC can crash on re-opening a qmake based project from session or enabling additional kit

I'm having some older sessions / settings used with the latest QC. When trying to open a project listed on the recent projects (or loading one of the sessions that contains this project) QC crashes inside the proparser.

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Microsoft Visual C++ Runtime Library
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Debug Error!

Program: C:\Qt\Qt5.9.3\5.9.3\msvc2015\bin\Qt5Cored.dll
Module: 5.9.3
File: D:\dev\qt-creator_curr\src\shared\proparser\ioutils.cpp
Line: 51

ASSERT: "fileName.isEmpty() || isAbsolutePath(fileName)" in file D:\dev\qt-creator_curr\src\shared\proparser\ioutils.cpp, line 51

(Press Retry to debug the application)

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Abort   Retry   Ignore   
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I think this is related to this specific project. It is basically a project created with QC a couple of months (or years?) ago.
The project's source files all look sane and I can easily use this project when doing a copy and removing the .user file.
The build directory that is set up inside the .user file does exist and contains the last successful build of this project.

Looking into the Makefile seems to reveal the problem: the original Qt that had been used to create the respective build does no more exist on the system. It feels like the proparser tries to run the qmake call again - but asserts when verifying the existence of the qmake file path?
I'd expect whenever opening an existing project fails (for whatever reason) QC prompts me whether to reconfigure it from scratch instead of crashing