Experimental bots layout tests fix: handle access to the frame 0 in case ther...

src/debug-debugger.js

Index: src/debug-debugger.js
===================================================================
--- src/debug-debugger.js	(revision 4250)
+++ src/debug-debugger.js	(working copy)
@@ -778,6 +778,8 @@
 ExecutionState.prototype.frame = function(opt_index) {
   // If no index supplied return the selected frame.
   if (opt_index == null) opt_index = this.selected_frame;
+  if (opt_index < 0 || opt_index >= this.frameCount())
+    throw new Error('Illegal frame index.');
   return new FrameMirror(this.break_id, opt_index);
 };