Relax ION heap size assertion to allow zero

Technically ION usage can be 0 if nothing uses it. Android emulator is
an example.

Bug: 167404539
Test: m cts
Change-Id: I20548ab6492a75e48426ca2c043ad32e6d0ced8b
1 file changed
tree: c240519c31d3aa261d842eda4eccbf68c0b7b918
  1. tests/