Trebuchet: Make remove workspace items of hidden apps optional

Change-Id: Id5c1f7a105d4140747a9f841b210cd7a7d1825df
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
Trebuchet: Fix NPE

Change-Id: I89c6a233e3480362db004d361914083223f3cb72
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>