Do the null deref guard before doing inlining, especially before doing type checks on the parameter…

tests/language/issue10783_test.dart

Index: tests/language/issue10783_test.dart
===================================================================
--- tests/language/issue10783_test.dart	(revision 0)
+++ tests/language/issue10783_test.dart	(revision 0)
@@ -0,0 +1,17 @@
+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// 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.
+
+import "package:expect/expect.dart";
+
+class C {
+  foo(int y) { return y; }
+}
+
+main() {
+  for (var b in [[false, 'pig']]) {
+    var c;
+    if (b[0]) c = new C();
+    Expect.throws(() => print(c.foo(b[1])), (e) => e is NoSuchMethodError);
+  }
+}