Add handling of empty stack in the backtrace debug request....

src/debug-delay.js

Index: src/debug-delay.js
===================================================================
--- src/debug-delay.js	(revision 960)
+++ src/debug-delay.js	(working copy)
@@ -832,10 +832,16 @@
 };
 
 
+ExceptionEvent.prototype.exception = function() {
+  return this.exception_;
+}
+
+
 ExceptionEvent.prototype.uncaught = function() {
   return this.uncaught_;
 }
 
+
 ExceptionEvent.prototype.func = function() {
   return this.exec_state_.frame(0).func();
 };
@@ -1322,6 +1328,14 @@
   // Get the number of frames.
   var total_frames = this.exec_state_.frameCount();
 
+  // Create simple response if there are no frames.
+  if (total_frames == 0) {
+    response.body = {
+      totalFrames: total_frames
+    }
+    return;
+  }
+
   // Default frame range to include in backtrace.
   var from_index = 0
   var to_index = kDefaultBacktraceLength;