Remove `BLI_assert(tc->sorted_index_map);` calls. Add one special case
in the function that investigates whether there is any selected item in
`tc->data`.
Earlier, I've been quite liberal in spreading these asserts around, to
guard against code paths that should have originally sorted `tc->data`
but by mistake didn't create `tc->sorted_index_map`.
They've been removed now, as they seem to be causing more trouble than
they're worth: the "sorting selected first" behaviour is only explicitly
there for proportional editing. With proportional editing disabled,
`tc->data` **only** contains selected items, and those are trivially
sorted first.
By now `tc->foreach_index_selected` can work without `sorted_index_map`;
if it is `nullptr`, it will assume that we're in the trivial case, and
that the array items can just be visited in index order.
Pull Request: https://projects.blender.org/blender/blender/pulls/141386
d4961dac0b