Fix Divide by zero possibility (ouch!)

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@4542 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_iax2.c

@@ -2868,9 +2868,12 @@ static unsigned int calc_timestamp(struct chan_iax2_pvt *p, unsigned int ts, str
 				* next multiple of frame size (so our
 				* silent periods are multiples of
 				* frame size too) */
+				if (f->samples / 8) /* check to make sure we dont core dump */
+				{
 					int diff = ms % (f->samples / 8);
 					if (diff)
 					    ms += f->samples/8 - diff;
+				}
 
 				p->nextpred = ms;
 				p->notsilenttx = 1;