Fix NPE when combining pop with add transaction.

Bug 35832085

When pop transactions and an add transaction are acting
in the same frame, optimized tranactions can work properly,
but unoptimized transactions have no guarantees. This tests
fixes for a crash with unoptimized transactions so they will
at least not break.

Test: ran fragment cts tests
Change-Id: I996f54ae2540f31134e6a9a28870826a73ea1610
1 file changed