AIP: Change default behavior for "Couldnt make a bibcode error"

[csgrant00]

python run.py -p "/proj/ads/abstracts/data/AIP/JATS.080723/APB/**/*xml

Issue is as follows:
This is a journal we are not currently loading (APL Bioengineering).

Current behavior, everything is output except %R which will cause shifting of assigned content to bibcodes for the rest of the file.

Suggested change:
put in a stub bibcode (e.g. bibstem="....." or XSTEM) so they won't mess up later content.