Review feedback.

- Better error message for unknown messageType.
- Remove unneeded if.

conformance/conformance_objc.m

@@ -78,16 +78,14 @@ static ConformanceResponse *DoTest(ConformanceRequest *request) {
       } else if ([request.messageType isEqual:@"protobuf_test_messages.proto2.TestAllTypesProto2"]) {
         msgClass = [TestAllTypesProto2 class];
       } else {
-        Die(@"Protobuf request doesn't have specific payload type");
+        Die(@"Protobuf request had an unknown message_type: %@", request.messageType);
       }
-      if (msgClass) {
       NSError *error = nil;
       testMessage = [msgClass parseFromData:request.protobufPayload error:&error];
       if (!testMessage) {
         response.parseError =
             [NSString stringWithFormat:@"Parse error: %@", error];
       }
-      }
       break;
     }