Fix Switch crash when onChange fires after view recycle (#59216)

Summary:
Fixes #59203.

`-[RCTSwitchComponentView onChange:]` dereferences `_eventEmitter` without checking it. `RCTViewComponentView -prepareForRecycle` resets `_eventEmitter`, and on iOS 26+ the redesigned `UISwitch` can deliver its `ValueChanged` action from a deferred `_UIAfterCACommitBlock` (e.g. after a drag/long-press). If the view gets recycled in between, `onChange:` runs on a recycled view and crashes with `EXC_BAD_ACCESS` inside `EventEmitter::dispatchEvent`.

This adds an early return when `_eventEmitter` is null, matching the existing guards in `RCTScrollViewComponentView`, `RCTImageComponentView`, `RCTModalHostViewComponentView` and `RCTVirtualViewComponentView`. Dropping the event is correct since the recycled view no longer represents that React node.

## Changelog:

[IOS] [FIXED] - Fix crash in `Switch` when `onChange` fires after the view has been recycled

Pull Request resolved: #59216

Test Plan:
- The crash is intermittent and timing-dependent (reported from production), so it is not reproducible on demand.
- The change is limited to an early-return null guard before the emitter dereference; normal toggling in RNTester's Switch examples is unaffected since `_eventEmitter` is set for mounted views.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed By: cipolleschi

Differential Revision: D126404965

Pulled By: javache

fbshipit-source-id: 5529c2f8d56cd9f9db5ea9f722e9e15794e2e8c1

Author: anvarbek

packages/react-native/React/Fabric/Mounting/ComponentViews/Switch/RCTSwitchComponentView.mm

@@ -110,6 +110,10 @@ - (void)onChange:(UISwitch *)sender
     return;
   }
 
+  if (!_eventEmitter) {
+    return;
+  }
+
   static_cast<const SwitchEventEmitter &>(*_eventEmitter)
       .onChange(SwitchEventEmitter::OnChange{.value = static_cast<bool>(sender.on)});
 }