Since the switch to slotted actions, we cannot solely rely on the Listbase of `curves` (this is for legacy actions only), but need to consider Channelbag for new slotted actions. There is `assigned_action_has_keyframes` that handles both of these and would also early out if we have no keyframes to process, so use it. Pull Request: https://projects.blender.org/blender/blender/pulls/135566