Fixes to import various Bay Area GTFS feeds.

A couple small fixes necessary for various Bay Area GTFS feeds (Caltrain, BART, VTA) to import.
I don't think I like this row. The catch is too general, and could catch rows with missing columns etc.
Isn't the solution of skipping empty rows in https://github.com/jarondl/pygtfs/pull/7/files#diff-37d894406fb18d5a282b4ac0a09aee96R72 enough?