vm: If popCount == _stack.Count in ExitBlock, just clear the stack an…

…d return

src/Std/Iteration.cs

@@ -601,6 +601,12 @@ public static RuntimeGenerator Repeat(RuntimeObject item, RuntimeInteger? n = nu
     public static RuntimeGenerator Reverse(IEnumerable<RuntimeObject> items)
         => new(items.Reverse());
 
+    [ElkFunction("reverseMut")]
+    public static void Reverse(RuntimeList items)
+    {
+        items.Values.Reverse();
+    }
+
     /// <param name="items">All items</param>
     /// <param name="count">The amount of items to skip from the left</param>
     /// <returns>A generator for the first n items.</returns>

src/Vm/InstructionExecutor.cs

@@ -655,14 +655,19 @@ private void UnpackUpper(byte count)
 
     private void ExitBlock(byte popCount)
     {
-        if (_stack.Count == 1)
+        if (_stack.Count == popCount)
+        {
+            while (_stack.Any())
+                Pop();
+
             return;
+        }
 
-        var returnValue = _stack.Pop();
+        var returnValue = _stack.PopObject() as RuntimeObject;
         for (byte i = 0; i < popCount; i++)
             Pop();
 
-        _stack.Push(returnValue);
+        _stack.Push(returnValue ?? RuntimeNil.Value);
     }
 
     private void Ret()