title: Type 'null' is not assignable to type 'number'
body: <p>I have UserID: number in my user.model.ts file and i have function to reset my form in user.component.ts.
  `</p>
  <pre><code>resetForm(form?: NgForm) {
      if(form!=null)
      form.resetForm();
      this.service.formData = {
        UserID : null,
        UserName: '',
        Password: '',
        confirmPass: '',
        FirstName: '',
        lastName: '',
        email: '',
        UserRole: ''
      }
    }
  </code></pre>
  <p>`
  I got error in UserID : null, Type null is not assignable to type 'number' .How to fix this issue?</p>