As of [Revision 66772](
https://bugs.ruby-lang.org/projects/ruby-trunk/repository/trunk/revisions/66772)
 `Proc.new` without giving a block emits `warning: tried to create Proc object without a block`.

This commit fixes cases where Rails test suit tickles this warning.

See CI logs:
https://travis-ci.org/rails/rails/jobs/487205819#L1161-L1190
https://travis-ci.org/rails/rails/jobs/487205821#L1154-1159
https://travis-ci.org/rails/rails/jobs/487205821#L1160-L1169
https://travis-ci.org/rails/rails/jobs/487205821#L1189
https://travis-ci.org/rails/rails/jobs/487254404#L1307-L1416
https://travis-ci.org/rails/rails/jobs/487254405#L1174-L1191