[youdie006]

Description

Marshal and Encoder.Encode panic on a []*T or [N]*T that contains a nil element: encodeArray passes the zero reflect.Value from walkValue to encodeStruct, which calls v.Type(). Unmarshal into [N]*T leaves the elements past the last record nil (as TestUnmarshal expects), so a round trip crashes:

var users [3]*User
csvutil.Unmarshal([]byte("Name,Age\nalice,30\nbob,25\n"), &users)
csvutil.Marshal(users)
// panic: reflect: call of reflect.Value.Type on zero Value

With this change a nil element writes no record, so the example returns "Name,Age\nalice,30\nbob,25\n", the same CSV it was decoded from. Writing an empty row or returning an InvalidEncodeError would also work if you prefer either; skipping is the one that round-trips.

Checklist

• Code compiles without errors
• Added new tests for the provided functionality
• All tests are passing (go test -race ./...; the new cases panic on master)
• Updated the README and/or documentation, if necessary

Written with AI assistance (Claude); I have reviewed the change.