Blender Git Loki

Fix T93338: Curve Guide force field crash

Caused by {rBcf2baa585cc8}.

For Curve Guide force fields to work, the `Path Animation` option has to
be enabled. With it disabled, we are lacking the necessary
`anim_path_accum_length` data initialized [done by
`BKE_anim_path_calc_data`] which `BKE_where_on_path` relies on since
above commit.

Now just check for this before using it - and return early otherwise.
Prior to said commit, `BKE_where_on_path` would equally return early
with a similar message, so that is expected behavior here.

Maniphest Tasks: T93338

Differential Revision: https://developer.blender.org/D13371