PPM: uninstall preview fix

4.3beta1 testing feedback, there was a report that if you click in the installed-packages area in the Puppy Package Manager, when there are no packages installed, an erroneous dialog window comes up asking if you want to uninstall ''.

That condition is now picked up, and a dialog box now comes up informing you that you have to install a package first, before you can uninstall anything.

Tags: woof