Warning when rake assets:precompile with Sprockets

[jonmchan]

Describe the bug Does anyone else receive the following warning when running rake assets:precompile with rails_admin setup to use sprockets?

W, [2023-03-03T06:53:23.282082 #890]  WARN -- : Removed sourceMappingURL comment for missing asset 'rails_admin/popper.js.map' from /usr/local/bundle/gems/rails_admin-3.1.1/vendor/assets/javascripts/rails_admin/popper.js
W, [2023-03-03T06:53:23.312343 #890]  WARN -- : Removed sourceMappingURL comment for missing asset 'rails_admin/bootstrap.js.map' from /usr/local/bundle/gems/rails_admin-3.1.1/vendor/assets/javascripts/rails_admin/bootstrap.js

Reproduction steps

1. Use rails_admin in sprockets mode.
2. Do not have yarn installed, use only sprockets and importmap
3. run rake assets:precompile

Expected behavior No warning

Additional context

• rails version: Rails 7.0.4.2
• rails_admin version: rails_admin-3.1.1
• rails_admin npm package version: NA
• full stack trace (if there's an exception)