Handle malformed gzip pcaps

[guedou]

Here is a fix for https://issues.oss-fuzz.com/issues/559397010

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.12%. Comparing base (77d9498) to head (24070b6).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5162   +/-   ##
=======================================
  Coverage   81.11%   81.12%           
=======================================
  Files         390      390           
  Lines       97736    97744    +8     
=======================================
+ Hits        79281    79290    +9     
+ Misses      18455    18454    -1     

Files with missing lines	Coverage Δ
scapy/utils.py	73.28% <100.00%> (+0.10%)	⬆️

... and 8 files with indirect coverage changes

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