Will I get an error if I try unscheduling a WP Cron scheduled task that wasn’t scheduled?

So yeah, it does give errors for trying to unschedule something that isn’t scheduled, but the answer is pretty easy and simple:

$timestamp = wp_next_scheduled( 'scheduled_hook' );
if ($timestamp) wp_unschedule_event( $timestamp, 'scheduled_hook' );

Since wp_next_scheduled will return false for unscheduled hooks, a simple if in front of the call to wp_unschedule_event will prevent it from being called it there’s nothing scheduled