With this error message Gerrit rejects to push a commit if the target ref in the push specification has an incorrect format (for example: /refs/for/master, refs/for//master).
To solve the problem you have to correct the target ref in the push specification. Depending on whether you want to push your commit with or without code review the ref format is different:
ref format for pushing a commit for code review:
If it was the intention to push a commit for code review the target ref in the push specification must be the project’s magical ref refs/for/'branch' (where branch must be replaced with the name of an existing branch to which you want to push your commit). Further details about how to push a commit for code review are explained at Create Changes).
Example for pushing a commit for code review to the master branch:
$ git push ssh://JohnDoe@host:29418/myProject HEAD:refs/for/master
ref format for directly pushing a commit (without code review):
If it was the intention to bypass code review and to push directly to a branch the target ref in the push specification must be the name of the branch to which you want to push. Further details about how to bypass code review are explained at Bypass Review.
Example for pushing a commit directly to the master branch (without code review):
$ git push ssh://JohnDoe@host:29418/myProject HEAD:master
Part of Gerrit Error Messages