Fix #128760: NLA bake action throws error

Caused by db6113048d

Above commit was accessing action properties which are only available if
experimental baklava is enabled.
Now check for this.

Pull Request: https://projects.blender.org/blender/blender/pulls/128762

scripts/modules/bpy_extras/anim_utils.py

@@ -364,7 +364,7 @@ def bake_action_iter(
             atd.use_tweak_mode = False
 
         atd.action = action
-        if action.is_action_layered:
+        if bpy.context.preferences.experimental.use_animation_baklava and action.is_action_layered:
             slot = action.slots.new(for_id=obj)
             atd.action_slot = slot