Minor fixes.

src/ifcblenderexport/blenderbim/bim/module/void/ui.py

@@ -1,6 +1,7 @@
 import bpy
 from bpy.types import Panel
 from blenderbim.bim.module.void.data import Data
+from blenderbim.bim.ifc import IfcStore
 
 
 class BIM_PT_voids(Panel):
@@ -11,6 +12,10 @@ class BIM_PT_voids(Panel):
     bl_region_type = "WINDOW"
     bl_context = "object"
 
+    @classmethod
+    def poll(cls, context):
+        return IfcStore.get_file()
+
     def draw(self, context):
         props = context.active_object.BIMObjectProperties
         if props.ifc_definition_id not in Data.products: