Fix the debugger for strict-mode functions.

src/mirror-debugger.js

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1587 matching lines @@
     result += '[debugger]';
   } else {
     // If the receiver has a className which is 'global' don't display it.
     var display_receiver = !receiver.className || receiver.className() != 'global';
     if (display_receiver) {
       result += receiver.toText();
     }
     // Try to find the function as a property in the receiver. Include the
     // prototype chain in the lookup.
     var property = GetUndefinedMirror();
-    if (!receiver.isUndefined()) {
-      for (var r = receiver; !r.isNull() && property.isUndefined(); r = r.protoObject()) {
+    if (receiver.isObject()) {
+      for (var r = receiver;
+           !r.isNull() && property.isUndefined();
+           r = r.protoObject()) {
         property = r.lookupProperty(func);
       }
     }
     if (!property.isUndefined()) {
       // The function invoked was found on the receiver. Use the property name
       // for the backtrace.
       if (!property.isIndexed()) {
         if (display_receiver) {
           result += '.';
         }
@@ skipping 797 matching lines @@
   }
   if (!NUMBER_IS_FINITE(value)) {
     if (value > 0) {
       return 'Infinity';
     } else {
       return '-Infinity';
     }
   }
   return value;
 }