Deprecated function: fwrite(): Passing null to parameter #2 ($data) of type string is deprecated in Masterminds\HTML5\Serializer\OutputRules->wr() (line 454 of /app/vendor/masterminds/html5/src/HTML5/Serializer/OutputRules.php)

I've created an issue in Masterminds/HTML5, asking them to upcast the function `fwrite` , then it fixes the error:

https://github.com/Masterminds/html5-php/issues/254

However, the problem is that this plugin is dependent on Drupal core. I am not sure if it's a core issue or $dom->nodeValue null has to be fixed here.

Hi @jkamizato
I wanted to take a look at this issue and I cannot reproduce it so far. However looking at the process() function code I presume that $dom->nodeValue is null when $text is empty - is that correct?
In such case we could simply add if statement at the beginning and return empty text without any processing if it is empty.