Add NoneType check for opts in modules.git.init

`opts` should default to '' in `git.init`, as is the case with all other functions in `modules.git`
Merge branch 'patch-2' of https://github.com/talwai/salt into talwai-patch-2
Lint fix
Merge pull request #15473 from thatch45/talwai-patch-2

Merge #15458 with lint fix