onloadwff.js error interfering with rendering of reCaptcha in a form

[neal-wilxite]

I am trying to render a reCAPTCHA widget in a "contact us" page using the following js:

<script>
 function enableSubmit(){...}
function disableSubmit(){..}

 $(function (){
        var onloadCallback = function() {
            grecaptcha.render('reCaptcha', {
                'sitekey' : [site_key],
                'theme' : 'light',
                'callback' : enableSubmit
            });
      };
      document.write('<script src="https://www.google.com/recaptcha/api.js?onload=onloadCallback&render=explicit"><\/script>');
});
</script>

The page throws this error:

onloadwff.js:71 Uncaught (in promise) TypeError: Cannot read property 'querySelectorAll' of null
    at s.<anonymous> (onloadwff.js:71)
    at l (onloadwff.js:71)
    at Object.next (onloadwff.js:71)
    at n (onloadwff.js:71)

Which seems to be due to the line starting "document.write.."

My details are below.

Lastpass extension V 4.53.0 Browser: Chrome 84 User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.125 Safari/537.36 Operating system: Windows 10 Javascript enabled: Yes Cookies enabled: Yes Flash version: Not installed Java version: Not installed Websockets supported: Yes WebGL supported: Yes Language: en-GB Browser size: 2543 x 1297 Screen size: 2560 x 1440 Color depth: 24 bit AdBlock enabled: Yes