Error message displayed in developer tools when extension is activated

[Eagle94T]

Hi there,
Thanks for the extension, it's doing a great job.

However, as soon as I activate the extension and I load a page I get an error displayed on the developer-console:
Unchecked runtime.lastError: The message port closed before a response was received.

How to reproduce

1. Open e.g. this link with activated extension: https://www.google.com/search?q=test
2. There should be the error in the console.
3. Deactivate the extension and reload the page or open it once again.
4. No error is displayed in the console.