Fix controller `can_insert` function returning number instead of boolean

[OgelGames]

Fixes a bug where items from tubes would always enter the drawer controller even when it can't accept them, causing items to get stuck in tubes.

An example setup: Items should go into the drawer controller if there is room, otherwise they go into the trash. Before this fix they would instead go back to the tube they came from, because the trash has a lower priority.

[lnjX]

Thanks :)