[Switch-Expression] Bad code generation for switch expression inside enum constructor results in ExceptionInInitializerError

The following program when compiled and run on master results in `ExceptionInInitializerError`:

```
public enum X {
ONE;
X() {
System.out.println(switch(this) {
default -> this;
});
}

public static void main(String [] args) {
X x = ONE;
System.out.println(x);
}
}
```

When run we get:
```
Exception in thread "main" java.lang.ExceptionInInitializerError
Caused by: java.lang.NullPointerException: Cannot read the array length because "" is null
at X.values(X.java:1)
at X.$SWITCH_TABLE$X(X.java:1)
at X.(X.java:4)
at X.(X.java:2)
```