fix: null dereference in get_SelectionContainer when no selection container exists (#16091)

* fix: null dereference in get_SelectionContainer when no container found

Agent-Logs-Url: https://github.com/microsoft/react-native-windows/sessions/dee66731-6253-459a-8ba1-f733d5bee554

Co-authored-by: vineethkuttan <66076509+vineethkuttan@users.noreply.github.com>

* Change files

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: vineethkuttan <66076509+vineethkuttan@users.noreply.github.com>

Author: Copilot

change/react-native-windows-0ddd05a5-b75b-423a-a461-6dcafc41d3b4.json

@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "fix: null dereference in get_SelectionContainer when no container found",
+  "packageName": "react-native-windows",
+  "email": "66076509+vineethkuttan@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}

vnext/Microsoft.ReactNative/Fabric/Composition/CompositionDynamicAutomationProvider.cpp

@@ -1064,6 +1064,11 @@ HRESULT __stdcall CompositionDynamicAutomationProvider::get_SelectionContainer(I
   *pRetVal = nullptr;
 
   auto selectionContainerView = GetSelectionContainer();
+  // Per UIA spec, returning S_OK with *pRetVal == nullptr is correct when the element
+  // is not contained within a selection container.
+  if (!selectionContainerView)
+    return S_OK;
+
   auto uiaProvider =
       winrt::get_self<winrt::Microsoft::ReactNative::implementation::ComponentView>(selectionContainerView)
           ->EnsureUiaProvider();