core: harden request.Request (#1009)

Check for a nil message and if we have a question section. Request is
usually called with an external Msg that already saw validation checks,
but we may also call it from message we create of our own, that may or
may not adhire to this. Just be more robust in this case.

This PR reverts a previous commit that was applied to master.

request/request_test.go

@@ -31,6 +31,35 @@ func TestRequestRemote(t *testing.T) {
 	}
 }
 
+func TestRequestMalformed(t *testing.T) {
+	m := new(dns.Msg)
+	st := Request{Req: m}
+
+	if x := st.QType(); x != 0 {
+		t.Errorf("Expected 0 Qtype, got %d", x)
+	}
+
+	if x := st.QClass(); x != 0 {
+		t.Errorf("Expected 0 QClass, got %d", x)
+	}
+
+	if x := st.QName(); x != "." {
+		t.Errorf("Expected . Qname, got %s", x)
+	}
+
+	if x := st.Name(); x != "." {
+		t.Errorf("Expected . Name, got %s", x)
+	}
+
+	if x := st.Type(); x != "" {
+		t.Errorf("Expected empty Type, got %s", x)
+	}
+
+	if x := st.Class(); x != "" {
+		t.Errorf("Expected empty Class, got %s", x)
+	}
+}
+
 func BenchmarkRequestDo(b *testing.B) {
 	st := testRequest()