If the value stack is empty, return null value instead of trying to index into an empty collection.

From: MeteorDevelopment/starscript#34

Author: GreemDev

src/Lib/Public/Hypervisor/Abstraction/AbstractHypervisor.Stack.cs

@@ -19,8 +19,15 @@ public partial class AbstractHypervisor<TSelf>
 
     protected void ClearStack() => _stack.Clear();
 
-    public Value Peek() => _stack.Peek();
-    public Value Peek(int offset) => _stack.Peek(offset);
+    public Value Peek() 
+        => _stack.Count is 0 
+            ? Value.Null 
+            : _stack.Peek();
+
+    public Value Peek(int offset) 
+        => _stack.Count <= offset 
+            ? Value.Null 
+            : _stack.Peek(offset);
 
     public bool PopBoolean(string error)
     {

src/Lib/Public/Util/TransparentStack.cs

@@ -37,4 +37,6 @@ public T Pop()
     public T Peek() => _buffer[_buffer.CurrentSize - 1];
 
     public T Peek(int offset) => _buffer[_buffer.CurrentSize - 1 - offset];
+
+    public int Count => _buffer.CurrentSize;
 }