fix one more warning missed because i did not have new enough libpri installed

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@153650 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_dahdi.c

@@ -11697,7 +11697,9 @@ static char *complete_span_helper(const char *line, const char *word, int pos, i
 
 	for (which = span = 0; span < NUM_SPANS; span++) {
 		if (pris[span].pri && ++which > state) {
-			asprintf(&ret, "%d", span + 1);	/* user indexes start from 1 */
+			if (asprintf(&ret, "%d", span + 1) < 0) {	/* user indexes start from 1 */
+				ast_log(LOG_WARNING, "asprintf() failed: %s\n", strerror(errno));
+			}
 			break;
 		}
 	}