fixes menu generation

molecularnodes/operators/node_add_buttons.py

@@ -96,6 +96,8 @@ def poll(self, context):
         # is associated with the object / molecule. If there isn't then the assembly
         # operator will be greyed out and unable to be executed
         obj = context.active_object
+        if obj is None:
+            return False
         return obj.mn.biological_assemblies != ""
 
     def execute(self, context):
@@ -135,6 +137,13 @@ class MN_OT_iswitch_custom(Operator):
     node_name: StringProperty(name="node_name", default="chain")  # type: ignore
     starting_value: IntProperty(name="starting_value", default=0)  # type: ignore
 
+    @classmethod
+    def poll(cls, context: Context) -> bool:
+        obj = context.active_object
+        if obj is None:
+            return False
+        return True
+
     @classmethod
     def description(cls, context, properties):
         return properties.description

molecularnodes/ui/menu.py

@@ -127,7 +127,11 @@ def menu(
         else:
             raise ValueError(f"Data type currently not supported: {self.dtype}")
         # test if the object has the currently tested property to enable operator
-        row.enabled = bool(context.active_object.get(self.property_id))
+        obj = context.active_object
+        if obj is None:
+            row.enabled = False
+        else:
+            row.enabled = bool(obj.get(self.property_id))
 
 
 class Break: