Fix error swallowing in InputConnectionCommand unparcelling

This is a follow up CL to my previous CL [1], which added
InputConnectionCommand class with parcelling support.

A Parcel object may contain multiple primitive and Parcelable values.
Neither shallowing exceptions nor early-returning null solves the
fundomental problem that any subsequent read from the same Parcel
object is at risk.

Just let the higher layer decide how to deal with it.

 [1]: I86eba7185b4b0664c1b0b3da794dfc5eeddc725c
      2757c248

Bug: 194151409
Fix: 194567417
Test: atest CtsInputMethodTestCases:InputConnectionEndToEndTest
Test: atest FrameworksCoreTests:InputConnectionCommandTest
Change-Id: Icd2b40e63771085cb8d88721fbdca7a089256b28