Don't crash on deserialized type inference.

pkg/compiler/lib/src/serialization/modelz.dart

Index: pkg/compiler/lib/src/serialization/modelz.dart
diff --git a/pkg/compiler/lib/src/serialization/modelz.dart b/pkg/compiler/lib/src/serialization/modelz.dart
index af70b04bb514c9a1300c7c794d03ec35aeb4add4..8927cb5f816802fde2b76e452fdeac081493743a 100644
--- a/pkg/compiler/lib/src/serialization/modelz.dart
+++ b/pkg/compiler/lib/src/serialization/modelz.dart
@@ -1861,8 +1861,13 @@ abstract class ParameterElementZ extends DeserializedElementZ
   @override
   FunctionSignature get functionSignature => _unsupported('functionSignature');
 
+  // TODO(johnniwinther): HACK. Remove [initializer] and [node] on
+  // [ParameterElementZ] when the inference does need these.
   @override
-  Expression get initializer => _unsupported('initializer');
+  Expression get initializer => null;
+
+  @override
+  Node get node => null;
 
   @override
   bool get isNamed => _decoder.getBool(Key.IS_NAMED);