Comment가 안 만들어집니다.

```package com.example.jun.myeongjuntalk.chat;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import com.example.jun.myeongjuntalk.R;

import com.example.jun.myeongjuntalk.model.ChatModel;

import com.google.firebase.auth.FirebaseAuth;

import com.google.firebase.database.DataSnapshot;

import com.google.firebase.database.DatabaseError;

import com.google.firebase.database.FirebaseDatabase;

import com.google.firebase.database.ValueEventListener;

public class MessageActivity extends AppCompatActivity {

private String destinationUid;

private EditText editText;

private String uid,chatRoomUid;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_message);
    uid = FirebaseAuth.getInstance().getCurrentUser().getUid();//채팅을 요구한 아이디, 즉 사용자 본인 단말기 아이디
    destinationUid = getIntent().getStringExtra("destinationUid");//채팅을 당하는 아이디
    Button button = (Button) findViewById(R.id.meesage_btn);
    editText = (EditText)findViewById(R.id.message_edt);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            ChatModel chatModel = new ChatModel();
            chatModel.users.put("uid",true);
            chatModel.users.put("destinationUid",true);
            if(chatRoomUid == null){
                Log.d(null,"되냐");
                FirebaseDatabase.getInstance().getReference().child("chattingRoom").push().setValue(chatModel);
            }
            else{
                Log.d(null,"되냐2");
                ChatModel.Comment comment = new ChatModel.Comment();
                comment.uid = uid;
                comment.message = editText.getText().toString();
                FirebaseDatabase.getInstance().getReference().child("chattingRoom").child(chatRoomUid).child("comments").push().setValue(comment);
            }
        }
    });
    checkRoom();
}
void checkRoom(){
    Log.d(null,"checkRoom");                                 //중복
    FirebaseDatabase.getInstance().getReference().child("chattingRoom").orderByChild("users/"+uid).equalTo(true).addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for(DataSnapshot item : dataSnapshot.getChildren()){
                ChatModel chatModel = item.getValue(ChatModel.class); //채팅방 테이블에 사용자와 대화상대의 uid를 가져옴
                if(chatModel.users.containsKey(destinationUid)){
                    chatRoomUid = item.getKey();
                }
            }
        }
        @Override
        public void onCancelled(DatabaseError databaseError) {
        }
    });
}

}

이 코드로 했을 때 , comment가 안 만들어집니다. 제가 볼 때는  
elss 문이 실행이 안되는 거 같습니다. chattingRoomId값을 가져와도 자꾸 널 값으로 되서 자꾸 if문만 실행됩니다.