When a catch is unreachable, use the canonical empty array instead of null as its type array.

runtime/vm/code_descriptors.cc

 // Copyright (c) 2012, 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.
 
 #include "vm/code_descriptors.h"
 
 namespace dart {
 
 void DescriptorList::AddDescriptor(RawPcDescriptors::Kind kind,
                                    intptr_t pc_offset,
@@ skipping 106 matching lines @@
       // Initialize it to some meaningful value.
       const bool has_catch_all = false;
       // Check it is uninitialized.
       ASSERT((list_[i].outer_try_index == -1) &&
              (list_[i].pc_offset == ExceptionHandlers::kInvalidPcOffset));
       handlers.SetHandlerInfo(i,
                               list_[i].outer_try_index,
                               list_[i].pc_offset,
                               list_[i].needs_stacktrace,
                               has_catch_all);
-      handlers.SetHandledTypes(i, Array::null_array());
+      handlers.SetHandledTypes(i, Array::empty_array());
     } else {
       const bool has_catch_all = ContainsDynamic(*list_[i].handler_types);
       handlers.SetHandlerInfo(i,
                               list_[i].outer_try_index,
                               list_[i].pc_offset,
                               list_[i].needs_stacktrace,
                               has_catch_all);
       handlers.SetHandledTypes(i, *list_[i].handler_types);
     }
   }
   return handlers.raw();
 }
 
 
 }  // namespace dart