Don't consider resources < 0 as invalid

The only invalid resource ID is '0'. All other resource IDs are
valid; even negative resource IDs.

With the introduction of namespaces in AAPT2, resource IDs start with
0x80, 0x81, ... [ie. because Java only supports signed types, they are
considered negative]. For app transition animations negative resource
IDs were incorrectly considered "invalid".

Change-Id: Ic8837975d8811826bb9b6635d44a0ac004daad36
Fixes: 70716301
Test: Manual. Run multi-split APK and see that transition animations work when defined in a split
Test: Manual. Open a textbox and see the keyboard animates correctly.