Program: 70541
Project: 70541
Buggy source:
@Nullable @Override public View onCreateView(@NonNull LayoutInflater inflater,@Nullable ViewGroup container,@Nullable Bundle savedInstanceState){
  bind=FragmentChatBinding.inflate(inflater);
  bind.chatList.setLayoutManager(new LinearLayoutManager(getContext()));
  adapter=new ChatAdapter(getContext());
  bind.chatList.setAdapter(adapter);
  auth=FirebaseAuth.getInstance();
  db=FirebaseDatabase.getInstance();
  db.getReference().child("String_Node_Str").child(auth.getCurrentUser().getUid()).child("String_Node_Str").addChildEventListener(new ChildEventListener(){
    @Override public void onChildAdded(    DataSnapshot dataSnapshot,    String s){
      final Chat chat=new Chat((String)dataSnapshot.getValue());
      db.getReference().child("String_Node_Str").child(chat.getChat_id()).child("String_Node_Str").limitToLast(1).addValueEventListener(new ValueEventListener(){
        @Override public void onDataChange(        DataSnapshot dataSnapshot){
          for (          DataSnapshot snap : dataSnapshot.getChildren()) {
            db.getReference().child("String_Node_Str").child((String)snap.getValue()).addListenerForSingleValueEvent(new ValueEventListener(){
              @Override public void onDataChange(              DataSnapshot dataSnapshot){
                chat.setLast_message((String)dataSnapshot.child("String_Node_Str").getValue());
                chat.setTime((String)dataSnapshot.child("String_Node_Str").getValue());
                db.getReference().child("String_Node_Str").child(chat.getChat_id()).child("String_Node_Str").addListenerForSingleValueEvent(new ValueEventListener(){
                  @Override public void onDataChange(                  DataSnapshot dataSnapshot){
                    for (                    DataSnapshot snap : dataSnapshot.getChildren())                     if (!auth.getCurrentUser().getUid().equals((String)snap.getValue())) {
                      db.getReference().child("String_Node_Str").child((String)snap.getValue()).child("String_Node_Str").addListenerForSingleValueEvent(new ValueEventListener(){
                        @Override public void onDataChange(                        DataSnapshot dataSnapshot){
                          chat.setChat_name((String)dataSnapshot.getValue());
                          adapter.update(chat);
                        }
                        @Override public void onCancelled(                        DatabaseError databaseError){
                        }
                      }
);
                      break;
                    }
                  }
                  @Override public void onCancelled(                  DatabaseError databaseError){
                  }
                }
);
              }
              @Override public void onCancelled(              DatabaseError databaseError){
              }
            }
);
            break;
          }
        }
        @Override public void onCancelled(        DatabaseError databaseError){
        }
      }
);
    }
    @Override public void onChildChanged(    DataSnapshot dataSnapshot,    String s){
    }
    @Override public void onChildRemoved(    DataSnapshot dataSnapshot){
    }
    @Override public void onChildMoved(    DataSnapshot dataSnapshot,    String s){
    }
    @Override public void onCancelled(    DatabaseError databaseError){
    }
  }
);
  return bind.getRoot();
}

Fixed version (ground truth):
@Nullable @Override public View onCreateView(@NonNull LayoutInflater inflater,@Nullable ViewGroup container,@Nullable Bundle savedInstanceState){
  bind=FragmentChatBinding.inflate(inflater);
  bind.chatList.setLayoutManager(new LinearLayoutManager(getContext()));
  adapter=new ChatAdapter(getContext());
  bind.chatList.setAdapter(adapter);
  auth=FirebaseAuth.getInstance();
  db=FirebaseDatabase.getInstance();
  db.getReference().child("String_Node_Str").child(auth.getCurrentUser().getUid()).child("String_Node_Str").addChildEventListener(new ChildEventListener(){
    @Override public void onChildAdded(    DataSnapshot dataSnapshot,    String s){
      final Chat chat=new Chat((String)dataSnapshot.getValue());
      db.getReference().child("String_Node_Str").child(chat.getChat_id()).child("String_Node_Str").addListenerForSingleValueEvent(new ValueEventListener(){
        @Override public void onDataChange(        DataSnapshot dataSnapshot){
          chat.setPhoto_url((String)dataSnapshot.getValue());
          db.getReference().child("String_Node_Str").child(chat.getChat_id()).child("String_Node_Str").limitToLast(1).addValueEventListener(new ValueEventListener(){
            @Override public void onDataChange(            DataSnapshot dataSnapshot){
              for (              DataSnapshot snap : dataSnapshot.getChildren()) {
                db.getReference().child("String_Node_Str").child((String)snap.getValue()).addListenerForSingleValueEvent(new ValueEventListener(){
                  @Override public void onDataChange(                  DataSnapshot dataSnapshot){
                    chat.setLast_message((String)dataSnapshot.child("String_Node_Str").getValue());
                    chat.setTime((String)dataSnapshot.child("String_Node_Str").getValue());
                    db.getReference().child("String_Node_Str").child(chat.getChat_id()).child("String_Node_Str").addListenerForSingleValueEvent(new ValueEventListener(){
                      @Override public void onDataChange(                      DataSnapshot dataSnapshot){
                        for (                        DataSnapshot snap : dataSnapshot.getChildren())                         if (!auth.getCurrentUser().getUid().equals((String)snap.getValue())) {
                          db.getReference().child("String_Node_Str").child((String)snap.getValue()).child("String_Node_Str").addListenerForSingleValueEvent(new ValueEventListener(){
                            @Override public void onDataChange(                            DataSnapshot dataSnapshot){
                              chat.setChat_name((String)dataSnapshot.getValue());
                              adapter.update(chat);
                            }
                            @Override public void onCancelled(                            DatabaseError databaseError){
                            }
                          }
);
                          break;
                        }
                      }
                      @Override public void onCancelled(                      DatabaseError databaseError){
                      }
                    }
);
                  }
                  @Override public void onCancelled(                  DatabaseError databaseError){
                  }
                }
);
                break;
              }
            }
            @Override public void onCancelled(            DatabaseError databaseError){
            }
          }
);
        }
        @Override public void onCancelled(        DatabaseError databaseError){
        }
      }
);
    }
    @Override public void onChildChanged(    DataSnapshot dataSnapshot,    String s){
    }
    @Override public void onChildRemoved(    DataSnapshot dataSnapshot){
    }
    @Override public void onChildMoved(    DataSnapshot dataSnapshot,    String s){
    }
    @Override public void onCancelled(    DatabaseError databaseError){
    }
  }
);
  return bind.getRoot();
}