Select chain during unwrap bug

When i try to select chain during unwrap i get this: Unknown command: /_SelChain
when typed by hand it works but when used on mesh rhino crashed

btw. when i want to unwrap mesh is there any command similar to select loop? it chould be sel chain but chain dont work on mesh at all

UV tools didnt get any update and are still very poor.

SR1 RC seems to fix this bug.