Fix nil-panic if repository has no default branch
Created by: mrnugget
This is the fix for the issue reported in https://github.com/sourcegraph/customer/issues/537.
The problem:
- Sometimes repositories don't have a default branch, because they're being cloned or updated by Sourcegraph. See code here:
git.DefaultBranch
- We skip the repositories with no repositories, but too late. With the introduction of
.batchignore
we added additional code that broke that check.