Error notice

Hi

So I changed the PHP version of a site I’m working on to 7.3 which caused the site to crash. I then reverted back to 5.6 which restored the site but now has the following message on every page

“Notice: Undefined offset: 1 in /home/aizerdesigner/public_html/wp-content/plugins/js_composer/include/classes/shortcodes/vc-custom-heading.php on line 136

Notice: Undefined offset: 2 in /home/aizerdesigner/public_html/wp-content/plugins/js_composer/include/classes/shortcodes/vc-custom-heading.php on line 137”

I understand this is a plugin issue but wonder if i could get a bit of guidance. I’m a designer, not a developer (clearly) so probably shouldnt have been messing. Basically I was asked to add some code for a tracker to the <header> and WP wouldnt allow it as I was on an old PHP version

Thanks
Andy

The page I need help with: [log in to see the link]