Raise an error if creating the MergeRequestDiff fails

app/models/merge_request.rb

@@ -668,7 +668,7 @@ class MergeRequest < ApplicationRecord
 
     # n+1: https://gitlab.com/gitlab-org/gitlab-ce/issues/37435
     Gitlab::GitalyClient.allow_n_plus_1_calls do
-      merge_request_diffs.create
+      merge_request_diffs.create!
       reload_merge_request_diff
     end
   end