NoMethodError: undefined method `raw_deltas' for nil:NilClass

Gitaly Conversation: gitaly#321 (closed)

https://sentry.gitlap.com/gitlab/gitlabcom/issues/47656/

NoMethodError: undefined method `raw_deltas' for nil:NilClass
  lib/gitlab/checks/change_access.rb:229:in `check_commit_diff'
    commit.raw_deltas.each do |diff|
  lib/gitlab/metrics/instrumentation.rb:156:in `block in check_commit_diff'
    trans.method_call_for(#{label.to_sym.inspect}).measure { super }
  lib/gitlab/metrics/method_call.rb:23:in `measure'
    retval = yield
  lib/gitlab/metrics/instrumentation.rb:156:in `check_commit_diff'
    trans.method_call_for(#{label.to_sym.inspect}).measure { super }
  lib/gitlab/checks/change_access.rb:171:in `block in push_rule_check'
    if error = check_commit_diff(commit, push_rule)
...
(145 additional frame(s) were not displayed)

NoMethodError: undefined method `raw_deltas' for nil:NilClass