Fix file uploader, test typed attributes

[bizley]

Q	A
Is bugfix?	✔️
New feature?	❌
Breaks BC?	✔️ see below
Fixed issues	#19855

Validator does not modify the attribute anymore - it was filtering out non-uploaded-files values from the array so far, but only for the array typed attributes with maxFiles != 1 or minFiles > 1. Setting max files != 1 and sending empty array does not ends in error.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 11 lines in your changes are missing coverage. Please review.

Project coverage is 13.51%. Comparing base (e1268d1) to head (1f618b6).

:exclamation: Current head 1f618b6 differs from pull request most recent head 7c5b213

Please upload reports for the commit 7c5b213 to get more accurate results.

Files	Patch %	Lines
framework/validators/FileValidator.php	0.00%	11 Missing :warning:

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #20167      +/-   ##
============================================
- Coverage     22.16%   13.51%   -8.66%     
+ Complexity    11386    11380       -6     
============================================
  Files           430      430              
  Lines         37113    37082      -31     
============================================
- Hits           8225     5010    -3215     
- Misses        28888    32072    +3184     

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[samdark]

Would you please add a line for CHANGELOG?

[samdark]

:+1: