fix(scanner): crash when scanning a METADATA file w/o appropriate data

[BreadGenie]

Fix #1300

[codecov-commenter]

Codecov Report

Merging #1301 (d69409f) into main (2d69f84) will decrease coverage by 0.07%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #1301      +/-   ##
==========================================
- Coverage   78.96%   78.89%   -0.08%     
==========================================
  Files         262      264       +2     
  Lines        4801     4813      +12     
  Branches      578      578              
==========================================
+ Hits         3791     3797       +6     
- Misses        856      862       +6     
  Partials      154      154              

Flag	Coverage Δ
longtests	78.89% <0.00%> (-0.08%)	⬇️

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Impacted Files	Coverage Δ
cve_bin_tool/version_scanner.py	74.30% <0.00%> (-1.59%)	⬇️
cve_bin_tool/async_utils.py	91.66% <0.00%> (-2.09%)	⬇️
cve_bin_tool/checkers/__init__.py	95.45% <0.00%> (ø)
test/test_data/pigz.py	100.00% <0.00%> (ø)
cve_bin_tool/checkers/pigz.py	100.00% <0.00%> (ø)

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