Fix bugs in checksum verify command

[IljaN]

Forward port of #33610

[phil-davis]

LGTM
Issue #33051 and sub-issue #33613 are pending for creating acceptance tests for this sort of stuff.

[codecov]

Codecov Report

Merging #33612 into master will increase coverage by <.01%.
The diff coverage is 85.71%.

@@             Coverage Diff              @@
##             master   #33612      +/-   ##
============================================
+ Coverage     64.22%   64.22%   +<.01%     
+ Complexity    18431    18269     -162     
============================================
  Files          1193     1193              
  Lines         69076    69077       +1     
  Branches       1277     1277              
============================================
+ Hits          44363    44364       +1     
  Misses        24341    24341              
  Partials        372      372

Flag	Coverage Δ	Complexity Δ
#javascript	52.91% <ø> (ø)	0 <ø> (ø)	⬇️
#phpunit	65.53% <85.71%> (ø)	18269 <0> (-162)	⬇️

Impacted Files	Coverage Δ	Complexity Δ
apps/files/lib/Command/VerifyChecksums.php	96.42% <85.71%> (+0.04%)	37 <0> (ø)	⬇️

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