Use jump-cut for invalid custom animation of embedded activity

App may pass zero resource as custom animation to skip animation.
For the case, return a no-op animation with duration 0, so the
ActivityEmbeddingAnimationRunner#createAnimator can get empty
adapters to perform the expected jump-cut.

This aligns the same behavior as non-embedded default case.

Fix: 308684712
Test: ActivityEmbeddingAnimationRunnerTests#testInvalidCustomAnimation

Change-Id: Ie62fc70a74319840ed197cee73ae9d37fa628971