Bad error message about undefined variable in UPDATE statement

[rekby]

Reproduce:

Execute yql:

CREATE TABLE t(id int64, val int64, primary key(id));

UPDATE t SET val = $asd;

Error:

contrib/ydb/library/yql/sql/v1/insert.cpp:394  BuildUpdateColumns(): requirement values failed, message: Invalid values node

Expected error: Unknown name: $asd