As you can see, this blank Commands lens is now on my Unity Launcher, without installing any related software. It launches the Run a command dialog (like Alt+F2) but it has no icon...how did it get there? Is it related to recent Unity updates? Or maybe to some application? If so, how can I get rid of it, since there's no file under /usr/share/unity/places? Thanks for your time!
What it is, is a bug. File a report on launchpad.net and gain some Karma. Attach that screenshot. :)
As for how you get rid of it, if you press alt+f2 and run compiz --replace, then I'm fairly sure it'll go away.
As a wild guess, I'd say "Commands" is the default label for launcher quicklists and that somehow, an empty and unconfigured launcher entry has been created for some reason. But it's a wild guess and it might very well be entirely wrong.
I experienced something similar. I tried to add a launchericon to the launcher, which was executing the xkill command. It worked but instead of a symbol there was a blank space, however by rightclicking and clicking keep in the launcher I could remover this issue.