Fix #118878: Anim: pinned bone custom properties not visible in edit-mode

Use `context.edit_bone` when available. This also properly accounts for
pinning of the armature.

scripts/startup/bl_ui/properties_data_bone.py

@@ -569,6 +569,10 @@ class BONE_PT_custom_props(BoneButtonsPanel, rna_prop_ui.PropertyPanel, Panel):
 
     @classmethod
     def _get_context_path(self, context):
+        if context.mode == 'EDIT_ARMATURE':
+            # This also accounts for pinned armatures.
+            return "edit_bone"
+
         obj = context.object
         if not obj:
             # We have to return _something_. If there is some bone by some