Maestro: MgCooker fails to run after unchecking Base Layer Group then selecting individual zoom levels

[jbirch]

When trying to set up an MgCooker task, I initially wanted to try with a single zoom level. In order to do this, I unchecked the "Base Layer Group" level to unselect all, and then checked the individual zoom level. When I click on Build Tiles Now, the dialog goes away.

I believe that this is happening because when I uncheck the "Base Layer Group" the Library level is also unchecked, but when I re-check a single layer the top level is not re-checked.