Fixes bug where animation duration and fps calculations were being

@bcbarsness Found the issue that broke transformTo and similar animations. Goes back to changes introduced in the asset cache merge.
Previously, animationMesh was undefined for cases with no animation meshes. New system results in zero length array.  Some animationMesh code was checking for just undefined, others were checking undefined _and_ nonzero length. One instance was just checking undefined, and led to the bug. Updated to fix by adding a length check at that point. (Argument could be made that leaving the animatedMesh value undefined instead of an empty array for the no mesh case could be preferable, it'd be easy enough to switch to that fix instead).


performed on animation meshes for objects without animation meshes,
leading to broken transformTo's and similar behavior. Fixes bug
by adding check for zero length arrays of animatedMesh.

Fixes #2675.