abc2midi do not handles all guitar chords.
In this case, it displays an error message with the name of not supported gchord.
It is possible to add to abc file a chord definition like %%MIDI chordname 7#5 0 4 8 10
The attached zip file contains a database of gchords no supported by abc2midi that you can select and copy in the abc files.
This database was made by "search and replace" on the file "chordtable.py" (part of mma program - http://www.mellowood.ca/mma/downloads.html
As my musical knowledge is very limited, it can be found some mistakes and omissions.
==Corrections and additions are welcome.==
P.S. : For linux users, the bash script "fetch-chords.sh" selects and inserts the missing gchords directly in the abc file
_COPY_ your abc file in the folder FetchChords.
In this directory simply type : sh fetch-chords.sh YourAbcFile.abc
Disclaimer : NO WARANTY - Make backup of your abc file before using the script.