fix: no such object error code

[BarryTong65]

Description

replace error code from 500 to 404 when object is not found

Rationale

"gater/object_handler.go:437","msg":"HttpStatusCode[500] action[GetObject] 
\"inner_code\":55001,\"description\":\"failed to get object info from consensus, 
error:rpc error: code = Unknown desc = No such object: unknown request\"

Example

add an example CLI or API response...

Changes

Notable changes:

• replace error code from 500 to 404 when object is not found

Potential Impacts

• QA