Catchable fatal error - within Visual Composer text-block window

Hi
just downloaded your theme and got this error straight away...

Catchable fatal error: Argument 1 passed to DOMNode::replaceChild() must be an instance of DOMNode, null given, called in /var/www/vhosts/conztruct.co.nz/httpdocs/wp-content/plugins/uncode-core/vc_extend/init.php on line 286 and defined in /var/www/vhosts/conztruct.co.nz/httpdocs/wp-content/plugins/uncode-core/vc_extend/init.php on line 365

The text-block within Visual Composer works when saved, just thought you'd like to know the error.

Great theme.

Would it have something to do with:
PHP Time Limit:
PHP Max Input Vars:

As i haven't increased these?

thanks