Second 'Make' build step added to imported project adds an empty argument

Create a very simple project: mkdir proj && touch proj/main.c proj/Makefile

Import that via Welcome -> + New Project -> Import Project (last) -> Import Existing Project (last)

After importing, go to Projects -> Build & Run / Build and in Build Settings (which by default has a make all config) click on "Add Build Step" -> "Make"

This now has the config Make: make '' all – notice the stray '' argument, which when running becomes an empty string that make does not like: empty string invalid as file name. Stop. This can not be removed anymore via the UI, the project.creator.user file has to be edited to delete corresponding <value type="QString"></value> entry manually.