This is a strange and inexplicable error. Typing into the Ubuntu dashboard spawns new tabs in Chromium. This happens even if Chromium is not running it simply launches and spawns one or more tabs.
Sometimes this also happened when software updater started.
I had Chromium as the default browser earlier and made Firefox the default to fix this problem. It did not work.
What worked was logging out and logging back into my Google chat account in Online Accounts.
No idea why this is so, but turns out that it is a Chromium bug and what I did intuitively (after trying many other things that didn’t work) was a fix.