be gentler on negative-offset reads - just do nothing instead of asserting.  from bao's review. (transplanted from 061b8b55838634425455ebc4ac046462dfc0e5f1)
be gentler on negative-offset reads - just do nothing instead of asserting.  from bao's review.
(transplanted from 061b8b55838634425455ebc4ac046462dfc0e5f1)

gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm