Resolve "Viewing a particular commit gives 500 error ~ Error (undefined method `binary?')"

What does this MR do?

Fixes a couple more cases where we might get a BatchLoader instance back and we expected the object itself to be falsey when nil.

Are there points in the code the reviewer needs to double check?

I think I got them all now - see https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16193 for the previous attempt.

Why was this MR needed?

Bug 😞

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Review
  • Has been reviewed by Backend

What are the relevant issue numbers?

Closes #44257 (closed).