As subtitles are added, kdenlive creates a [projectname].srt file. If the default subtitle sequence is removed, kdenlive seams to create an empty [projectname].srt file. After the project is saved, closed and reopened, kdenlive crashes. Problem an be solved by removing 0-byte [projectname].srt file.
I cannot reproduce the crash with version 23.08.4, following your steps. Does it still happen with the latest version?
yes now with version 23.08.4 it does not crash anymore!