Merge "interval == 0" workaround from personal rework branch, still need to…

Merge "interval == 0" workaround from personal rework branch, still need to investigate why wanpipe does not provide this information (and if 20ms is a good default value)

git-svn-id: http://svn.openzap.org/svn/openzap/trunk@699 a93c3328-9c30-0410-af19-c9cd2b2d52af

libs/openzap/src/ozmod/ozmod_isdn/ozmod_isdn.c

@@ -1490,10 +1490,11 @@ static void *zap_isdn_tones_run(zap_thread_t *me, void *obj)
 			break;
 		}
 	}
+	if (!interval) {
+		interval = 20;
+	}
 	zap_log(ZAP_LOG_NOTICE, "Tone generating interval %d\n", interval);
 
-	assert(interval != 0);
-
 	/* init teletone */
 	teletone_init_session(&ts, 0, teletone_handler, dt_buffer);
 	ts.rate     = 8000;