perf(files): Prevent extraneous requests when tree children are loading

[Pytal]

Summary

• Prevents identical requests if the children are already loading

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)