If the `transdata_check_local_islands` check does not succeed, we end up
with `CTX_NO_PET` for scaling/rotation.
For `Grease Pencil`, this was lost in the transition from GPv2 > GPv3
(type was renamed to "legacy", then removed from
`transdata_check_local_islands` in a804320138, but the new type was
never added).
Curves never specified support for this, but both types are (in theory)
taking into account `V3D_AROUND_LOCAL_ORIGINS` in
`curve_populate_trans_data_structs` (logic from 9d86fada03 might be a
bit broken for proportional editing "islands" without anything selected
as reported in #139101, but that will be corrected in another PR).
So to resolve, add `Grease Pencil` and `Curves` as supported object
types in `transdata_check_local_islands`
NOTE: `transdata_check_local_center` already has these two types as
well.
Part of #139101
Pull Request: https://projects.blender.org/blender/blender/pulls/139209
1d0c11987f