Fix RspecProfiling if ENV not present
What does this MR do and why?
This MR fixes an issue where the ENV for RspecProfiling
does not exist.
$ bundle exec rake gitlab:db:migration_testing:sample_batched_background_migrations:ci | tee tmp/migration-testing/ci/background_migrations/full-batched-migration-output.log || true
rake aborted!
TypeError: no implicit conversion of nil into String
/gitlab/config/initializers/rspec_profiling.rb:106:in `dirname'
/gitlab/config/initializers/rspec_profiling.rb:106:in `block in <main>'