Chrome Addons Error in chrome.runtime.sendMessage

[DerTudi]

I have this files for a Chrome Addon, which has to click a few XPaths with delays, then goes a page back and this will be repeated the whole time! But if i Click on the Start button at the Popup HTML , i get the error in the Developer Section:
"Error in chrome.runtime.sendMessage: [object Object]" Context
popup.html
Stacktrace
popup.js:42 (Anonym Function)

popup.txt
popupHTML.txt
background.txt
content.txt
manifest.txt

What should I do ? ... Thanks for your help!