Have the opt. compiler set the size of "empty" frames to zero.

This is to mimic Quick's behavior and honor stack frame
alignment constraints after changes introduced by Change-Id
I0fdb31e8c631e99091b818874a558c9aa04b1628.

This issue use to make oatdump crash on oat files produced by
the optimized compiler (e.g.
out/host/linux-x86/framework/x86_64/core-optimizing.oat).

Change-Id: I8ba52601edb0a0993eaf8923eba55aafdce5043e