res_rtp_multicast: Fix SEGV in ast_multicast_rtp_create_options

ast_multicast_rtp_create_options now checks for NULL or empty options

Change-Id: Ib845eae46a67a9787e89a87ebd1027344e5e0362

res/res_rtp_multicast.c

@@ -143,7 +143,7 @@ struct ast_multicast_rtp_options *ast_multicast_rtp_create_options(const char *t
 
 	mcast_options = ast_calloc(1, sizeof(*mcast_options)
 			+ strlen(type)
-			+ strlen(options) + 2);
+			+ strlen(S_OR(options, "")) + 2);
 	if (!mcast_options) {
 		return NULL;
 	}
@@ -155,8 +155,9 @@ struct ast_multicast_rtp_options *ast_multicast_rtp_create_options(const char *t
 	mcast_options->type = pos;
 	pos += strlen(type) + 1;
 
-	/* Safe */
-	strcpy(pos, options);
+	if (!ast_strlen_zero(options)) {
+		strcpy(pos, options); /* Safe */
+	}
 	mcast_options->options = pos;
 
 	if (ast_app_parse_options(multicast_rtp_options, &mcast_options->opts,