Let's say the git status command returns the following.

~]$ git status
On branch master
Your branch is based on 'origin/master', but the upstream is gone.
  (use "git branch --unset-upstream" to fixup)

nothing to commit, working tree clean

This can occur when you have created a new repository using the git init command with the --bare flag and you are adding and commit the very first file to the empty repository. In this scenario, the error should no longer appear after you have committed and pushed the very first file to the new repository.