Check the instance of ADDR_ENTRY[0]

[guedou]

This PR fixed an issue reported by OSS-Fuzz.

I reduced the original reproducer to minimize the bytes added to the test cases.

[gpotter2]

Test is failing

[guedou]

They are passing locally. I will debug this.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 80.68%. Comparing base (6f0faf3) to head (d7b4c7a). Report is 28 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4565      +/-   ##
==========================================
- Coverage   81.61%   80.68%   -0.94%     
==========================================
  Files         356      356              
  Lines       85545    85574      +29     
==========================================
- Hits        69819    69045     -774     
- Misses      15726    16529     +803     

Files with missing lines	Coverage Δ
scapy/layers/netbios.py	92.75% <100.00%> (ø)

... and 27 files with indirect coverage changes