error message when using Features

When adding features to the ad I have to use the add button to store it. This way, in addition to storing the feature, another empty field is added to add a new feature. This way I will always end up with an empty featur field.
So when I save the ad, I get a blank page with an error message “bool(false) bool(false)”. Actually everything is stored perfectly, I would still like to fix this problem because many operators get stuck when they see a blank page, not everyone understands that you just have to go back with the browser key.