Cardslib: Fix possible NPE on customsource loader

in corner cases it can happen that the bitmapWorkerTask.customSource is allready
null before we want to cancel it. Prevent this issue and check against null.

Change-Id: I64342656ae1510f3555de79ce7e46c224cbe6b76
Cardslib: change again the default expand button pressed

to fit kitkat style better. Due that this lib is used here in an
API 19 environmente

Change-Id: I70f0f9b324230c5cc49be5f118109a4b00507a17