Image errors (php7?)

Hi,

I developed a website on php 5.6 and your plugin works like a charm.
Now I migrate the site to production environment with PHP7 and if I try to load an image for header I get this error in console:
Uncaught TypeError: Cannot read property 'url' of undefined
In generated PDF, also, instead of images I have a little red cross.

It could be a PHP7 issue or something else?

Thanks!