For the Normalize Weights operator, dynamically set the default 'Subset'
parameter so that it is applicable to the current context.
When the user's last use of Normalize Weights was set to "Deform Pose
Bones", and then tries to use the operator on a mesh without armature,
Blender would try to use the previous opertor properties and show an
error message. This is resolved by switching to `WT_VGROUP_ACTIVE` in
such cases.
Reviewed By: zanqdo, sybren
Maniphest Tasks: T95038
Differential Revision: https://developer.blender.org/D14961
0f22b5599a