Panic when using mun build

```rust
pub  fn fact(n: usize) -> usize {
   	if n == 0 {return 1} else {n * x(n-1)}
}
```

This panics here https://github.com/TheDan64/inkwell/blob/master/src/module.rs#L1383

Removing the `return` keyword  or adding `return` in the else clause fixes the issue.