Remove special casing of == null

pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart

Index: pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
diff --git a/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart b/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
index 2a25e1a900fa33e0d59125249bf0b4e6e4696465..ae2cd8d1ce87c468772def4bfe3872a4f9bcdd45 100644
--- a/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
+++ b/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
@@ -580,7 +580,12 @@ class KernelAstTypeInferenceMap implements KernelToTypeInferenceMap {
     if (send.name.name == '[]=') {
       return closedWorld.commonMasks.dynamicType;
     }
-    return _resultOf(_target).typeOfSend(_astAdapter.getNode(send));
+    ast.Node node = _astAdapter.getNodeOrNull(send);
+    if (node == null) {
+      assert(send.name.name == '==');
+      return closedWorld.commonMasks.dynamicType;
+    }
+    return _resultOf(_target).typeOfSend(node);
   }
 
   TypeMask typeOfGet(ir.PropertyGet getter) {