In Grease Pencil, when using the tools in Sculpt Mode and Vertex Paint
mode, the check on editable layers wasn't entirely accurate. There was
a strict check on an editable _active_ layer, but since the tools work
on _all_ editable layers, the check should be wider: if there is _any_
editable layer, the tool can work.
That is fixed in this PR. Now the tools can be used when, for example,
a layer group is active or when the active layer is hidden, but there
are other editable layers present.
In Vertex Paint mode there was an additional issue: with Auto Keying
enabled, a new keyframe was created for the active layer only. A new
keyframe should be created for _every_ editable layer. As is the case
now with this PR.
Pull Request: https://projects.blender.org/blender/blender/pulls/140119
ab1b451250