spatial decomposition ui - use poll_message_set instead of .enabled

To give user more descriptive message about what's wrong.

src/bonsai/bonsai/bim/module/spatial/operator.py

@@ -270,6 +270,18 @@ class DeleteContainer(bpy.types.Operator, tool.Ifc.Operator):
     bl_options = {"REGISTER", "UNDO"}
     container: bpy.props.IntProperty()
 
+    @classmethod
+    def poll(cls, context):
+        props = tool.Spatial.get_spatial_props()
+        active_container = props.active_container
+        if not active_container:
+            cls.poll_message_set("No active container.")
+            return False
+        if active_container.ifc_class == "IfcProject":
+            cls.poll_message_set("Cannot delete IfcProject.")
+            return False
+        return True
+
     def _execute(self, context):
         core.delete_container(tool.Ifc, tool.Spatial, tool.Geometry, container=tool.Ifc.get().by_id(self.container))
 
@@ -332,6 +344,18 @@ class SetDefaultContainer(bpy.types.Operator):
     bl_description = "Set this as the default container that all new elements will be contained in"
     container: bpy.props.IntProperty()
 
+    @classmethod
+    def poll(cls, context):
+        props = tool.Spatial.get_spatial_props()
+        active_container = props.active_container
+        if not active_container:
+            cls.poll_message_set("No active container.")
+            return False
+        if active_container.ifc_class == "IfcProject":
+            cls.poll_message_set("Cannot set default IfcProject as default container.")
+            return False
+        return True
+
     def execute(self, context):
         core.set_default_container(tool.Spatial, container=tool.Ifc.get().by_id(self.container))
         core.set_orientation_slot(tool.Spatial, container=tool.Ifc.get().by_id(self.container))

src/bonsai/bonsai/bim/module/spatial/ui.py

@@ -143,10 +143,8 @@ class BIM_PT_spatial_decomposition(Panel):
             op.part_class = self.props.subelement_class
 
             row = self.layout.row(align=True)
-            non_ifc_project_active = self.props.active_container.ifc_class != "IfcProject"
 
             col = row.column(align=True)
-            col.enabled = non_ifc_project_active
             op = col.operator("bim.set_default_container", icon="OUTLINER_COLLECTION", text="Set Default")
             op.container = ifc_definition_id
 
@@ -155,7 +153,6 @@ class BIM_PT_spatial_decomposition(Panel):
             col.operator("bim.select_container", icon="OBJECT_DATA", text="").container = ifc_definition_id
 
             col = row.column(align=True)
-            col.enabled = non_ifc_project_active
             op = col.operator("bim.delete_container", icon="X", text="")
             op.container = ifc_definition_id