Fix --separate flag

[LoukasPap]

Fixes separate file processing when using the --separate flag.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.19%. Comparing base (d7a713e) to head (8d6fab9).

Files with missing lines	Patch %	Lines
src/sed/processor.rs	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #384      +/-   ##
==========================================
- Coverage   82.25%   82.19%   -0.06%     
==========================================
  Files          13       13              
  Lines        5522     5526       +4     
  Branches      310      310              
==========================================
  Hits         4542     4542              
- Misses        977      981       +4     
  Partials        3        3              

Flag	Coverage Δ
macos_latest	82.88% <0.00%> (-0.07%)	⬇️
ubuntu_latest	82.98% <0.00%> (-0.07%)	⬇️
windows_latest	0.00% <0.00%> (ø)

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