2 more solutions I had luck with when neither tab close + reopening the page in another tab nor closing all tabs in Chrome (and the browser) then restarting it didn't work:
1) I fixed it on my machine by closing the tab, force-closing Chrome, & restarting the browser without restoring tabs (Note: on a computer running CentOS Linux).
2) My boss (also on CentOS) had the same issue (alerts are a big part of my company's Javascript debugging process for numerous reasons e.g. legacy), but my 1st method didn't work for him. However, I managed to fix it for him with the following process:
a) Make an empty text file called FixChrome.sh, and paste in the following bash script:
#! /bin/bash
cd ~/.config/google-chrome/Default //adjust for your Chrome install location
rm Preferences
rm 'Current Session'
rm 'Current Tabs'
rm 'Last Session'
rm 'Last Tabs'
b) close Chrome, then open Terminal and run the script (bash FixChrome.sh).
It worked for him. Downside is that you lose all tabs from your current & previous session, but it's worth it if this matters to you.