Delegate RPCs on non-delegate accounts either succeed or fail with obscure error messages.

1. Create a new tz1 address (unrevealed)
2. Send address some funds (0.5 tez)
3. Check balance of address using context/delegates

curl --verbose http://127.0.0.1:18732/chains/main/blocks/head/context/delegates/tz1MYBu9pNB3SmFY47hiVCBhPsxpp8P2J93b
...
< HTTP/1.1 500 Internal Server Error
< content-length: 100
< content-type: application/json
<
[{"kind":"temporary","id":"proto.009-PsFLoren.tez.subtraction_underflow","amounts":["0","500000"]}]

But then why does this work?

curl --verbose http://127.0.0.1:18732/chains/main/blocks/head/context/delegates/tz1MYBu9pNB3SmFY47hiVCBhPsxpp8P2J93b/balance
...
< HTTP/1.1 200 OK
< content-type: application/json
< transfer-encoding: chunked
<
"500000"