If you tried restarting and that didn’t work to allow you to empty Trash, then you will need to boot into Recovery and disable SIP (System Integrity Protection). Once SIP disabled, you should be able to empty Trash. Recommend you re-enable SIP afterwards.
I would delete the Trash (Bin) folder from Terminal #3 , but I remember someone posted on the forum that moving Install macOS Mojave.app into /private/var/tmp/ and rebooting solved the problem.
Now, I moved the app to /private/var/tmp/ and it's no longer in the Bin. Thanks, bogdanw.
That's the good news; the bad news is, even after restarting, if I attempt to delete it completely, once in the Bin, it stays there. But at least, it's not an obstacle for emptying the Bin anymore.
Sorry, I misremembered, not in /private/var/tmp/.
Move the Install macOS Mojave.app into /private/tmp/ and restart. It should be automatically deleted.