Fix crash in observatory: stub code do not have inlined intervals information.

runtime/vm/object.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/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 12622 matching lines @@
   // If the code has stackmaps, it must have them for all safepoints.
   UNREACHABLE();
   return Stackmap::null();
 }
 
 
 void Code::GetInlinedFunctionsAt(
     intptr_t offset, GrowableArray<Function*>* fs) const {
   fs->Clear();
   const Array& intervals = Array::Handle(inlined_intervals());
+  if (intervals.IsNull()) {
+    // E.g., for code stubs.
+    return;
+  }
   Smi& start = Smi::Handle();
   Smi& end = Smi::Handle();
   Function& function = Function::Handle();
   for (intptr_t i = 0; i < intervals.Length(); i += Code::kInlIntNumEntries) {
     start ^= intervals.At(i + Code::kInlIntStart);
     if (!start.IsNull()) {
       end ^= intervals.At(i + Code::kInlIntEnd);
       if ((start.Value() <= offset) && (offset < end.Value())) {
         function ^= intervals.At(i + Code::kInlIntFunction);
         fs->Add(&Function::ZoneHandle(function.raw()));
@@ skipping 7974 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart