test(adif): assert FREQ_RX reaches the forwarded record too

The fix filled both halves of the receive side, but the test only proved
BAND_RX came out the other end. FREQ_RX is the half the question was
really about.

rxdefaults_test.go

@@ -20,10 +20,15 @@ func TestFillRXDefaults(t *testing.T) {
 	if q.FreqRXHz == nil || *q.FreqRXHz != hz {
 		t.Errorf("FreqRXHz = %v, want %d", q.FreqRXHz, hz)
 	}
-	rec := adif.SingleRecordADIF(q)
-	if !strings.Contains(strings.ToUpper(rec), "<BAND_RX:3>20M") {
+	// Assert on the RECORD another logger reads, not merely on the struct:
+	// both halves of the receive side have to reach it.
+	rec := strings.ToUpper(adif.SingleRecordADIF(q))
+	if !strings.Contains(rec, "<BAND_RX:3>20M") {
 		t.Errorf("BAND_RX missing from the forwarded record:\n%s", rec)
 	}
+	if !strings.Contains(rec, "<FREQ_RX:9>14.074000") {
+		t.Errorf("FREQ_RX missing from the forwarded record:\n%s", rec)
+	}
 }
 
 // A genuine split contact keeps what it was given.