cgen: fix option if expr with noreturn fn call (fix #22467)

[yuyi98]

This PR fix option if expr with panic() call (fix #22467).

• Fix option if expr with panic() call.
• Add test.

fn main() {
	mut x := ?string(none)
	x = if true {
		''
	} else {
		panic('')
	}
	println(x)
}

PS D:\Test\v\tt1> v run .
Option('')

[spytheman]

Excellent work.