title: ExtJs Checkbox Bind Issue
body: <p>A checkbox in ExtJs Form Panel is not binding properly , i.e when the value is changed from checked(value is 1) to unchecked (value is 0) the value in model for the respective field is still checked(1). This issue occurs in version 6.2.0.981, but the issue is not reproducible in latest version 6.2.1.167. Here is the fiddle for the same, toggle between the versions and check the issue. please let us know if there are any workaround for this issue in 6.2.0.981 version. Also in release notes of 6.2.1.167 its told that "EXTJS-21886 - Checkboxes don't return the correct value" is fixed, but how to have this fix in previous versions? </p>
  
  <p><a href="https://fiddle.sencha.com/#view/editor&amp;fiddle/1v08" rel="nofollow noreferrer">CheckBox Bind issue Fiddle</a></p>