Merge Request Created with `remove_source_branch` false fails on 9.2
Summary
On GitLab 9.2 when creating an MR through the API, GitLab throws a 500
Steps to reproduce
Use the documentation here: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/api/merge_requests.md#L289
Create an MR with "remove_source_branch: false"
What is the current bug behavior?
/usr/local/share/gems/gems/gitlab-4.0.0/lib/gitlab/request.rb:80:in `validate': Server responded with code 500, message: 500 Internal Server Error. Request URI: https://itromgit01.q8int.com/api/v4/projects/3/merge_requests (Gitlab::Error::InternalServerError)
from /usr/local/share/gems/gems/gitlab-4.0.0/lib/gitlab/request.rb:49:in `post'
from /usr/local/share/gems/gems/gitlab-4.0.0/lib/gitlab/client/merge_requests.rb:50:in `create_merge_request'
from /usr/local/share/gems/gems/gitlab-4.0.0/lib/gitlab.rb:25:in `method_missing'
from ./gitlab_create_merge_request.rb:91:in `<main>'
What is the expected correct behavior?
An MR created with the Remove source branch
box unchecked.