http 500 should not be returned if an index is already built

Run the following commands:

CREATE PRIMARY INDEX gamesim_primary on `gamesim-sample` USING GSI
(Wait for the index to be built)
BUILD INDEX ON `gamesim-sample`(gamesim_primary) USING GSI

The build index command returns an error that says that the index is built, but the HTTP error code is 500. This is incorrect because HTTP 500 means that something went wrong in the server. This is not what happened. The server properly executed this query and returned an error code.It seems this return code should be 200 since the request was processed successfully.