Fix switch statements with only default

If a switch statement only has a "default" case it will be replaced
with an expression that is just the default body and a break label.

Author: SeeminglyScience

src/PSLambda/CompileVisitor.cs

@@ -802,6 +802,15 @@ public object VisitSwitchStatement(SwitchStatementAst switchStatementAst)
             {
                 using (_loops.NewScope())
                 {
+                    if (switchStatementAst.Clauses.Count == 0)
+                    {
+                        return new[]
+                        {
+                            switchStatementAst.Default.Compile(this),
+                            Label(_loops.Break)
+                        };
+                    }
+
                     var clauses = new SwitchCase[switchStatementAst.Clauses.Count];
                     for (var i = 0; i < clauses.Length; i++)
                     {