Explicitly set default values for fields of ShadowNodeUpdateInfo (#54194)

Summary:
Pull Request resolved: #54194

Explicitly set default values for fields of ShadowNodeUpdateInfo

changelog: [internal] internal

Reviewed By: cortinico

Differential Revision: D84954459

fbshipit-source-id: 0b2fc7d35ec8e515db91f86cea85bb78cf746cd1

Author: mdvacca

packages/react-native/ReactCommon/react/renderer/uimanager/UIManagerUpdateShadowTree.cpp

@@ -26,7 +26,7 @@ struct ShadowNodeUpdateInfo {
   int depth;
   std::weak_ptr<const ShadowNode> node;
   // populate for node that needs props update
-  std::optional<folly::dynamic> changedProps;
+  std::optional<folly::dynamic> changedProps{};
   // populate for node that's also a ancestor node for updated nodes
   std::vector<int> updatedChildrenIndices{};
 };