Fix type error with `?` in existing code.
Fix type error with `?` in existing code.

graydon/rust,aidancully/rust,GBGamer/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,GBGamer/rust,graydon/rust,graydon/rust,graydon/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust