Address without delegations returns 500

[lukitsbrian]

Summary of Bug

When querying the endpoint cosmos/staking/v1beta1/delegations/${address} it throws an error with code 500 if there are no delegations for the address, which leads to unnecessary error catching on client-side applications.

Rather, I would expect a response 200 with an empty array such as what is provided in the cosmos/staking/v1beta1/delegators/${address}/unbonding_delegations endpoint, or a 404.

Version

gaia 4.1.0
cosmos-sdk 0.42.1

Steps to Reproduce

# new address
gaiad keys add testing

# 200 response with empty array in response
curl -s -w "\nstatus: %{http_code}" https://cosmos.sg-1.online/cosmos/staking/v1beta1/delegators/$(gaiad keys show testing -a)/unbonding_delegations

# 500 response with error
curl -s -w "\nstatus: %{http_code}" https://cosmos.sg-1.online/cosmos/staking/v1beta1/delegations/$(gaiad keys show testing -a)

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[alexanderbez]

I'd opt for a 404 here. Was there a reason we chose 500 @AmauryM or is this a bug?

[amaury1093]

In the gRPC handler, we return a NotFound error, which is imo 100% correct:

cosmos-sdk/x/staking/keeper/grpc_query.go

Lines 284 to 288 in 33e7297

	if delegations == nil {
	return nil, status.Errorf(
	codes.NotFound,
	"unable to find delegations for address %s", req.DelegatorAddr)
	}

My guess is this might be a gRPC-gateway error: codes.NotFound is translated into a 500 instead of a 404. @aleem1314 or @atheeshp do you know about this?

[atheeshp]

I'm not sure, will take a look.