If you’re in a rush just mash those buttons:
In plain english - remove the
sha you’re getting in error message from
.git/shallow file. You supposedly have a shallow copy of a repository and
in that mode git sends contents of
.git/shallow to remote you’re pulling from
so that it knows what to send down the internet pipes. And one of those lines in
shallow file is referencing an object that has been GCed from the repository.