Explicitly set default values for fields of ShadowViewNodePair (#54193)

Summary:
Pull Request resolved: #54193

Explicitly set default values for fields of ShadowViewNodePair

changelog: [internal] internal

Reviewed By: cortinico

Differential Revision: D84954458

fbshipit-source-id: 7ca2ed92d5622cf4dc01088d4e53b946d1bbd279

Author: mdvacca

packages/react-native/ReactCommon/react/renderer/mounting/internal/ShadowViewNodePair.h

@@ -18,7 +18,7 @@ namespace facebook::react {
  * This is not exposed to the mounting layer.
  */
 struct ShadowViewNodePair final {
-  ShadowView shadowView;
+  ShadowView shadowView{};
   const ShadowNode* shadowNode;
 
   /**