Editing merge request of a deleted fork results in undefined method `protected_branch?' for nil:NilClass
From gitlab-org/gitlab-ce#19197
https://sentry.gitlap.com/gitlab/gitlabcom/issues/7983/
NoMethodError: undefined method `protected_branch?' for nil:NilClass
app/models/merge_request.rb:310:in `can_remove_source_branch?'
!source_project.protected_branch?(source_branch) &&
lib/gitlab/metrics/instrumentation.rb:152:in `block in can_remove_source_branch?'
trans.measure_method(#{label.inspect}) { super }
lib/gitlab/metrics/method_call.rb:23:in `measure'
retval = yield
lib/gitlab/metrics/transaction.rb:71:in `measure_method'
@methods[name].measure(&block)
lib/gitlab/metrics/instrumentation.rb:152:in `can_remove_source_branch?'
trans.measure_method(#{label.inspect}) { super }
...
(177 additional frame(s) were not displayed)
ActionView::Template::Error: undefined method `protected_branch?' for nil:NilClass
app/models/merge_request.rb:310:in `can_remove_source_branch?'
!source_project.protected_branch?(source_branch) &&
lib/gitlab/metrics/instrumentation.rb:152:in `block in can_remove_source_branch?'
trans.measure_method(#{label.inspect}) { super }
lib/gitlab/metrics/method_call.rb:23:in `measure'
retval = yield
lib/gitlab/metrics/transaction.rb:71:in `measure_method'
@methods[name].measure(&block)
lib/gitlab/metrics/instrumentation.rb:152:in `can_remove_source_branch?'
trans.measure_method(#{label.inspect}) { super }
...
(177 additional frame(s) were not displayed)