- Pass Dart_Null() instead of an empty array for unused import maps.

bin/gen_snapshot.cc

Index: bin/gen_snapshot.cc
===================================================================
--- bin/gen_snapshot.cc	(revision 5138)
+++ bin/gen_snapshot.cc	(working copy)
@@ -274,12 +274,11 @@
   } else {
     // Load a dummy script as the script to setup the tag handler.
     Dart_Handle empty_string = Dart_NewString("");
-    Dart_Handle import_map = Dart_NewList(0);
-    Dart_Handle lib = Dart_LoadScript(empty_string,
+    library = Dart_LoadScript(empty_string,
                                       empty_string,
                                       BuiltinLibraryTagHandler,
-                                      import_map);
-    USE(lib);
+                                      Dart_Null());
+    VerifyLoaded(library);
     // This is a generic dart snapshot which needs builtin library setup.
     library = LoadGenericSnapshotCreationScript(Builtin::kBuiltinLibrary);
     VerifyLoaded(library);