fix: guard against nil responses (#243)

Signed-off-by: Chris Gianelloni <[email protected]>

Author: wolf31o2

internal/dns/dns.go

@@ -297,6 +297,9 @@ func stateRecordToDnsRR(record state.DomainRecord) (dns.RR, error) {
 }
 
 func copyResponse(req *dns.Msg, srcResp *dns.Msg, destResp *dns.Msg) {
+	if srcResp == nil {
+		return
+	}
 	// Copy relevant data from original request and source response into destination response
 	destResp.SetRcode(req, srcResp.MsgHdr.Rcode)
 	destResp.RecursionDesired = req.RecursionDesired
@@ -345,6 +348,9 @@ func doQuery(msg *dns.Msg, address string, recursive bool) (*dns.Msg, error) {
 	if err != nil {
 		return nil, err
 	}
+	if resp == nil {
+		return nil, fmt.Errorf("dns response empty")
+	}
 	slog.Debug(
 		fmt.Sprintf(
 			"response: rcode=%s, authoritative=%v, authority=%s, answer=%s, extra=%s",