Warning: Undefined array key and access array offset on value

Problem/Motivation

I encounter the following errors when saving an event entity.

Warning: Undefined array key "field_room" in intercept_event_node_event_form_validate() (line 886 of modules/contrib/intercept/modules/intercept_event/intercept_event.module).

Warning: Trying to access array offset on value of type null in intercept_event_node_event_form_validate() (line 886 of modules/contrib/intercept/modules/intercept_event/intercept_event.module).