Minor As suggested by tusefomal in MDL-81742, the Feedback module does not have a manager class. This class would avoid different weird scenarios like using $DB global in output classes.
Create a manager class with (at least) a has_feedback_items() | has_questions() to avoid a direct call to $DB->record_exists('feedback_item', ['feedback' => $this->feedback->id]) in mod_feedback\output\edit_action_bar