Maestro: selecting a new category in the New Resource dialog doesn't deselect the current template

[jbirch]

With the 3.0 preview, selecting a template changes the description and enables the Add button. When you change categories, a template is no longer selected, but the description remains set to the previously selected template and the Add button remains active. Clicking on the Add button causes an exception.

I would suggest clearing the description and disabling the Add button when switching categories.

As an aside, the dialog is called "New Resource", but the context menu item is "New Item"

[jng]

Fixed r5315