fix: search in this folder only crashes (500)

[fsbraun]

Description

When selecting "Search in this folder only" in a non-root folder, the search crashes.

Also adds a prefetch to optimize folder db hits (only minor improvement).

Related resources

• ...

• ...

Checklist

• [ ] I have opened this pull request against master
• [ ] I have added or modified the tests when changing logic
• [ ] I have followed the conventional commits guidelines to add meaningful information into the changelog
• [ ] I have read the contribution guidelines and I have joined #workgroup-pr-review on Slack to find a “pr review buddy” who is going to review my pull request.

[codecov[bot]]

Codecov Report

Merging #1366 (899c9b7) into master (548cb3f) will decrease coverage by 0.03%. The diff coverage is 25.00%.

@@            Coverage Diff             @@
##           master    #1366      +/-   ##
==========================================
- Coverage   73.63%   73.61%   -0.03%     
==========================================
  Files          74       74              
  Lines        3399     3400       +1     
  Branches      551      551              
==========================================
  Hits         2503     2503              
- Misses        725      726       +1     
  Partials      171      171              

Impacted Files	Coverage Δ
filer/admin/folderadmin.py	72.67% <25.00%> (-0.11%)	:arrow_down: