Fix analyzer's handling of import prefixes not followed by '.'.

tests/language/conditional_property_access_test.dart

 // Copyright (c) 2015, 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.
 
 // Verify semantics of the ?. operator when it does not appear on the LHS of an
 // assignment.
 
 // SharedOptions=--enable-null-aware-operators
 
 import "package:expect/expect.dart";
@@ skipping 29 matching lines @@
   // generated in the case of e1?.id.
   Expect.equals(null, nullC()?.bad); /// 05: static type warning
   { B b = new C(1); Expect.equals(1, b?.v); } /// 06: static type warning
 
   // Consequently, '?.' cannot be used to access static properties of classes.
   Expect.throws(() => C?.staticField, noMethod); /// 07: static type warning
   Expect.throws(() => h.C?.staticField, noMethod); /// 08: static type warning
 
   // Nor can it be used to access toplevel properties in libraries imported via
   // prefix.
-  Expect.throws(() => h?.topLevelVar, noMethod); /// 09: static type warning
+  var x = h?.topLevelVar; /// 09: compile-time error
 
   // However, '?.' can be used to access the hashCode getter on the class Type.
   Expect.equals(C?.hashCode, (C).hashCode); /// 10: ok
   Expect.equals(h.C?.hashCode, (h.C).hashCode); /// 11: ok
 }