PyAPI: require a unique_id for bl_ui.generic_ui_list

An empty unique_id would generate a warning when drawing.

scripts/startup/bl_ui/generic_ui_list.py

@@ -29,7 +29,7 @@ def draw_ui_list(
         context,
         class_name="UI_UL_list",
         *,
-        unique_id="",
+        unique_id,
         list_path,
         active_index_path,
         insertion_operators=True,
@@ -46,7 +46,7 @@ def draw_ui_list(
     :type context: :class:`Context`
     :arg class_name: Name of the UIList class to draw. The default is the UIList class that ships with Blender.
     :type class_name: str
-    :arg unique_id: Optional identifier, in case wanting to draw multiple unique copies of a list.
+    :arg unique_id: Unique identifier to differentiate this from other UI lists.
     :type unique_id: str
     :arg list_path: Data path of the list relative to context, eg. "object.vertex_groups".
     :type list_path: str

scripts/templates_py/ui_list_generic.py

@@ -20,6 +20,7 @@ class MyPanel(bpy.types.Panel):
             context,
             list_path="scene.my_list",
             active_index_path="scene.my_list_active_index",
+            unique_id="my_list_id",
         )