Broken img link in the accurate graphs, transfer graphs, hystorical graphs pages

I have two systems running observium one in our own production and the the other one is a clean install which I freshly installed for one of our clients.

after a update we noticed that the images are not working properly. When I viewed this page the first there was a notice about JPGraph to be installed. So I installed JPGraph like instructed and deleted the theme lines in jpg-config.php, still the same result.

we noticed that the images on our production system on the pages below:

• http://portal.a2b-internet.com/bill/bill_id=3/view=accurate/
• http://portal.a2b-internet.com/bill/bill_id=3/view=transfer/
• http://portal.a2b-internet.com/bill/bill_id=3/view=history/

See images attached.

When I add the &debug=1 parameter to the url I saw a jpgrapgh message, JpGraph Error: 25082 Illegal sizes specified for width or height when creating an image, (width=0, height=0)

Looking is my logs I found:
PHP Warning: Division by zero in /opt/observium/html/pages/bill/infoboxes.inc.php on line 27, referer: http://xxx.yyy.zzz.xxx/bill/bill_id=1/view=accurate/tab=monthly/&debug=1

looking into the code of that file it doesn't make really sense what I am looking for, since lines 27 tells me something about calculating the % used ....