SetupWizard: Fix a few possible NPEs

* Accessing SparseArrays with zero-based indexes can fail due to non-used
  indexes
* mCheckBoxes and mRows should always be accessed with the key they were
  added
-> use keyAt(index) when iterating the SparseArray
-> use the simSlotIndex when iterating the subInfoRecords

BUGBASH-318
BUGBASH-610 (partially)

Change-Id: Ib831c3623dafa5bd7d0c95acfa69f4a686644be6