Prevent task in recents being empty when activity info in unavailable

When an app is unavailable to get its activity info, it will not have a
color, title or icon and it would look weird in recents. Therefore skip
adding it to the recents list when this occurs.

Test: manual
Change-Id: I1cf2f7f8ea5ce132159f6aabfbfae31df0187660
Fixes: 64236158