Keeping the assign field empty auto-assigns the ToDo.

[AayushChaudhary0001]

If the user has already assigned any ToDo to any other user, then on creating the next ToDo and keeping the assign field empty auto-assigns the ToDo to the last ToDo assigned user.

Steps to reproduce:-

1. Create and assign the ToDo to any desired user.
2. Create a new ToDo.
3. Open the assign modal.
4. Keep it empty and click on assign button.

The ToDo would be auto-assigned to the user to whom previous ToDo was assigned.