UI: Don't save defaults in oldSettings in properties

The default settings were saved in the oldSettings variable of the
properties dialog in `86eb7ae` to be able to restore default settings in
undo/redo, but this doesn't actually do anything.
Besides this, it introduced a bug where clicking "Cancel" in the
properties dialog would save all settings, including default ones, as
well as a bug where not changing anything in the properties dialog would
still add an undo action.

UI/window-basic-properties.cpp

@@ -79,10 +79,7 @@ OBSBasicProperties::OBSBasicProperties(QWidget *parent, OBSSource source_)
 	obs_data_release(oldSettings);
 
 	OBSData nd_settings = obs_source_get_settings(source);
-	OBSData settings = obs_data_get_defaults(nd_settings);
-	obs_data_apply(settings, nd_settings);
-	obs_data_apply(oldSettings, settings);
-	obs_data_release(settings);
+	obs_data_apply(oldSettings, nd_settings);
 	obs_data_release(nd_settings);
 
 	auto handle_memory = [](void *vp, obs_data_t *old_settings,