Upgrading to GitLab Mattermost in GitLab 8.9

I may have a particular issue.
I have an instance of gitlab which when I installed, I set up mattermost but didn't use it at the time.
Now that I've upgraded gitlab and plan to use it, I run the interactive upgrade but it says I have 0 teams (expected), but I can't do the upgrade because I can't choose any team for the script to keep running. Any help, thoughts?