Steps to reproduce the issue

Joomla 4.0.0 beta 1 admin console.
Resize window to half the size of my MacBook Pro... ok I know you can't do that, so you are going to have to just drag the right side of your browser to make a smaller window...

yeah yeah I know, "The web was meant to be read, not squished. This isn't the way to test a responsive design. - Agree or disagree I dont care" but here we are..

Do whatever you need to to replicate this on a smaller screen...

Expected result

no blank dropdown

Actual result

three dots leading to a blank dropdown

System information (as much as possible)

replicated today on a Mac with safari "squashed" to half the screen real estate on a MacBook Pro 15"

Additional comments

It seems that if you go even smaller screen this dotted-menu drops to the bottom and is then populated with Private Messages and Post Installation messages - so its a useful menu, but there is a breakpoint where its unpopulated, at the top still and no use.