Always call fillItems

The fillItems has as side-effect that mListId is set in the 
ShoppingItemsViewer.
This field must be set to the correct list, otherwise the database
record of 'contains' will not get the correct list-id field.

The test TestShoppingActivity#testIntentAddItemsFromArrayList 
failed before this commit, and now passes.
Merge pull request #7 from RuthAlk/master

Description is a bit broad, but code looks reasonable. Thanks!