Get rid of old code for union/intersection in HType.

sdk/lib/_internal/compiler/implementation/universe/universe.dart

Index: sdk/lib/_internal/compiler/implementation/universe/universe.dart
diff --git a/sdk/lib/_internal/compiler/implementation/universe/universe.dart b/sdk/lib/_internal/compiler/implementation/universe/universe.dart
index e2a679d107f5ba505d60fd3815799e9971161182..53902f44041535f5e01aeac14bfb9ad5465a2a05 100644
--- a/sdk/lib/_internal/compiler/implementation/universe/universe.dart
+++ b/sdk/lib/_internal/compiler/implementation/universe/universe.dart
@@ -459,7 +459,7 @@ class TypedSelector extends Selector {
               selector.argumentCount,
               selector.namedArguments) {
     // Invariant: Typed selector can not be based on a malformed type.
-    assert(!identical(mask.base.kind, TypeKind.MALFORMED_TYPE));
+    assert(mask.isEmpty || !identical(mask.base.kind, TypeKind.MALFORMED_TYPE));
     assert(asUntyped.mask == null);
   }
 
@@ -504,6 +504,12 @@ class TypedSelector extends Selector {
       return appliesUntyped(element, compiler);
     }
 
+    if (mask.isEmpty) {
+      if (!mask.isNullable) return false;
+      return hasElementIn(compiler.backend.jsNullClass, element)
+          && appliesUntyped(element, compiler);
+    }
+
     // TODO(kasperl): Can't we just avoid creating typed selectors
     // based of function types?
     Element self = mask.base.element;