Make sure we throw the right NSM error when indexing out of range of a variable that can be null.

sdk/lib/_internal/lib/js_helper.dart

Index: sdk/lib/_internal/lib/js_helper.dart
===================================================================
--- sdk/lib/_internal/lib/js_helper.dart	(revision 27429)
+++ sdk/lib/_internal/lib/js_helper.dart	(working copy)
@@ -776,9 +776,11 @@
  * Called by generated code to throw an index-out-of-range exception,
  * for example, if a bounds check fails in an optimized indexed
  * access.  This may also be called when the index is not an integer, in
- * which case it throws an illegal-argument exception instead, like [iae].
+ * which case it throws an illegal-argument exception instead, like
+ * [iae], or when the receiver is null.
  */
-ioore(index) {
+ioore(receiver, index) {
+  if (receiver == null) receiver.length; // Force a NoSuchMethodError.
   if (index is !int) iae(index);
   throw new RangeError.value(index);
 }