Theme does not support soft-mandatory questions

[seccanj]

The new LimeSurvey 5 soft-mandatory questions, when not answered, show a popup message allowing the user to either return to the survey and fulfill the missing questions or continue without answering.

With skelvanilla, the custom popup window only contains a "Close" button (corresponding to the option to return to the survey and complete the unanswered questions), thus not allowing the user to continue without answering.

This way, soft-mandatory questions cannot be used.