Silence `Uncaught (in promise) Error: No tab with id: 182.`

[fregante]

It's possible that a new target is created and destroyed between the time it's detected and the the last file is injected. This shouldn't cause console noise because it's not a real error.

[fregante]

Also due to:

• "Error: The tab was closed." if tab closes while injecting content-scripts-register-polyfill#62

[fregante]

Second part in: fregante/webext-content-scripts@fc638bd

Last part missing:

• Update webext-content-scripts
• Update content-scripts-register-polyfill to v4 #54

I'm waiting to do this because the polyfill had a major release I don't want to update it together with #41, which is also a major change here.