Impossible to invoke a method ("getLink") on a null variable.

[mark-chief]

In craft 4, I am getting this error when using the below code.

Impossible to invoke a method ("getLink") on a null variable.

{{ block.cta.getLink({
  class: 'cta cta-light',
 }) }}

The field is in a Matrix > Supertable >Matrix structure.

{{ block.cta }} outputs the URL ok.

Thanks