can pop an unexisted property

tiramisu/api.py

@@ -683,6 +683,7 @@ class TiramisuContextProperty(TiramisuContext):
     @count
     def pop(self, prop):
         props = self.get()
+        if prop in props:
             props.remove(prop)
             self.set(frozenset(props))
             self.config_bag.setting_properties = self.config_bag.config.cfgimpl_get_settings().get_context_properties()