I have the old revision of QtCreator for test reasons. it's c839fe0e196da566486a8be03b1a9af1ce507c53
I can open it just fine. But if I open qtcreator.pro and add a space in the end I get many errors from qmake parsing .pro files.
This is the output - https://pastebin.com/bqqUq7Ha
The biggest problem here that all project parts become invalid so many things depending on it may become broken.