stasis_channels.c: Add null check for referred_by in ast_ari_transfer_message_create

When handling SIP transfers via ARI, the `referred_by` field in
`transfer_ari_state` may be null, since SIP REFER requests are not
required to include a `Referred-By` header. Without this check, a null
value caused the transfer to fail and triggered a NOTIFY with a 500
Internal Server Error.

diff --git a/main/stasis_channels.c b/main/stasis_channels.c
index 4e712e03ae91ada4dd154fa39dbeb0694b52b464..76173aa35212cd614592bfba0c5aa8177be16046 100644 (file)
--- a/main/stasis_channels.c
+++ b/main/stasis_channels.c
@@ -1797,11 +1797,14 @@ struct ast_ari_transfer_message *ast_ari_transfer_message_create(struct ast_chan
                }
        }
 
-       msg->referred_by = ast_strdup(referred_by);
-       if (!msg->referred_by) {
-               ao2_cleanup(msg);
-               return NULL;
+       if (referred_by) {
+               msg->referred_by = ast_strdup(referred_by);
+               if (!msg->referred_by) {
+                       ao2_cleanup(msg);
+                       return NULL;
+               }
        }
+
        ast_copy_string(msg->destination, exten, sizeof(msg->destination));
        msg->protocol_id = ast_strdup(protocol_id);
        if (!msg->protocol_id) {