Fix disabled move and indent buttons for the WBS tree manipulation

These icons are disabled when the WBS is showed filtered, as the manipulation
operations could be ambiguous or problematic, but it was treating wrongly
empty predicates.

FEA: ItEr77S15FilteringEnhancements
Fix wrong behaviour of projects list filtering

The component that shows the filtering results is adding the unscheduled projects when they
are not excluded by the dates range, but they were appearing also when they were not matching
the combobox conditions.

FEA: ItEr77S15FilteringEnhancements