Slimrecents: catch IllegalStateException for sw/hw rendering

When double-tapping the recents button fast to open last app, we
sometimes get a java.lang.IllegalStateException, saying
"Software rendering doesn't support hardware bitmaps"
and crashing SystemUI.

Since user didn't want to see any app thumbnails and a SystemUI crash is
bad, just ignore it

Change-Id: Ib8ba0a31d827b7b26871ea6a2c34be38056c3813