Fix inner scope guard indent

[nhojb]

Commit 25e41ed broken indentation of guard statements when nested within an inner scope. It's been bugging me for a while 😄

This PR fixes the indentation.

Before:

func main() {
    guard foo else {
    // wrong indentation
    }
}

After:

func main() {
    guard foo else {
        // correct indentation
    }
}

[taku0]

LGTM. Thank you!