The issue was that the summary channel was marked as
possible to do NLA mapping in `ANIM_nla_mapping_allowed`.
When it comes to doing the actual mapping it would silently do nothing
though because `bAnimListElem.adt` is always a `nullptr` for the summary.
However in `action_select.cc:580` the `KED_F1_NLA_UNMAP`
and `KED_F2_NLA_UNMAP` flags were already removed.
Those flags tell the summary line to do NLA mapping in `keyframes_edit.cc:368`.
(We may be able to remove those in the future)
The fix is to ensure that the summary line is
recognized as unable to do NLA mapping. That makes sense to
me at least because the summary line points to data but in itself
does not know about the NLA.
As a side effect, this also fixes circle select.
Pull Request: https://projects.blender.org/blender/blender/pulls/140664
32d2bc0a59