500 Internal Server Error in database_api.list_comments

{
	"jsonrpc":"2.0", 
	"method":"database_api.list_comments", 
	"params": { "start": ["gtg", "2016-09-01T01:01:01", "", ""], "limit": p, "order": "by_author_last_update" }, 
	"id":1
}

500 Internal Server Error
Server got itself in trouble

when invalid limit value (string)