Sometimes the extension doesn't work at all and no error messages are displayed

[captainbrosset]

Try this:

• make sure the extension is installed
• open a tab on https://addons.mozilla.org/en-US/firefox/
• open the toolbox on the extension panel
• type something

No results are shown.

Opening the addon debugger (via about:debugging), the following error is shown:

Can't send message to content script, port not open background.js:28:5
	sendToContentScript moz-extension://0b5c3e28-2ff4-594c-b2f2-35630b312b5c/background_scripts/background.js:28:5
	<anonymous> moz-extension://0b5c3e28-2ff4-594c-b2f2-35630b312b5c/background_scripts/background.js:23:3

This happens if the content script didn't load for some reason.
My suspicion for now is that this particular page define CSP headers, and that prevents the content script from being injected.

We should show an error message in the panel to warn users. Or better yet, find a way to fix this.