Body of POST to validators endpoint not filtering correctly

[mcdee]

Describe the bug
Against a goerli node:

curl -X POST -H 'content-type: application/json' --data '{"ids":["1"],"statuses":["active_ongoing"]}' http://localhost:5052/eth/v1/beacon/states/head/validators
{"execution_optimistic":false,"finalized":false,"data":[{"index":"1","balance":"35198517881","status":"active_ongoing","validator":{"pubkey":"0xaffc434cf8138634a4cd0ef6cb815febd3db25760b1b6c522f9b4aa78e599b60336d7dd2e953192e45d4ac91f66f0723","withdrawal_credentials":"0x00fc40352b0a186d83267fc1342ec5da49dbb78e1099a4bd8db16d2c0d223594","effective_balance":"32000000000","slashed":false,"activation_eligibility_epoch":"0","activation_epoch":"0","exit_epoch":"18446744073709551615","withdrawable_epoch":"18446744073709551615"}}]}

This looks good, however removing the status results in nothing returned:

curl -X POST -H 'content-type: application/json' --data '{"ids":["1"]}' http://localhost:5052/eth/v1/beacon/states/head/validators
{"execution_optimistic":false,"finalized":false,"data":[]}

In addition, an empty request also returns nothing:

curl -X POST -H 'content-type: application/json' --data '{}' http://localhost:5052/eth/v1/beacon/states/head/validators
{"execution_optimistic":false,"finalized":false,"data":[]}

According to the API docs "The lists of validator IDs and statuses to filter on. Either or both may be null to signal that no filtering on that attribute is desired." so I would expect to see 1 validator returned in the second request, and all of them in the third request.

[tersec]

#5762