Extraction of `FASTA` adds unnecessary `.pdb` extension if absent, which leads to inconsistensies

[valentynbez]

I.e., when I extract FASTA from afdb_swissprot_v4:

foldcomp_id = AF-B1YUJ2-F1-model_v4
fasta_header = AF-B1YUJ2-F1-model_v4.pdb

When I extract FASTA from my personal db:

foldcomp_id = MIP_00183643.pdb
fasta_header = MIP_00183643.pdb

I cannot use FASTA headers to query the database consistently.