Fix compiler crash when we declare several (global) variables, but only define some of them.

tests/compiler/dart2js_extra/multi_global_def_single_instantiation_test.dart

Index: tests/compiler/dart2js_extra/multi_global_def_single_instantiation_test.dart
diff --git a/tests/language/accessor_conflict_getter.dart b/tests/compiler/dart2js_extra/multi_global_def_single_instantiation_test.dart
similarity index 86%
copy from tests/language/accessor_conflict_getter.dart
copy to tests/compiler/dart2js_extra/multi_global_def_single_instantiation_test.dart
index 5b8d72fad773b7cf48fd0e0f9b40c3cd8669628d..a88ad9bed1b39e628a656eb2454ee88a23fbf7e2 100644
--- a/tests/language/accessor_conflict_getter.dart
+++ b/tests/compiler/dart2js_extra/multi_global_def_single_instantiation_test.dart
@@ -2,6 +2,5 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-var getValue;
-
-get x => getValue;
+var y, w, z, x = [];
+main() => x;