Fix prototype check in AnimatedObject.js (#54820)

Summary:
`isPlainObject` function defined in `AnimatedObject.js` doesn't handle `Object.create(null)` correctly.

this will throws when encountering objects with null prototype:

```js
Object.getPrototypeOf(Object.create(null)).isPrototypeOf(Object)
// TypeError: Cannot read properties of null (reading 'isPrototypeOf')
```

This breaks compatibility with libraries that use `Object.create(null)` for creating clean dictionary objects.

## Changelog:

[GENERAL] [FIXED] - Handle `Object.create(null)` correctly in AnimatedObject.js' `isPlainObject` function

Pull Request resolved: #54820

Test Plan:
```
import { isPlainObject } from 'react-native/Libraries/Animated/nodes/AnimatedObject';

// Before: throws TypeError
// After: returns true
isPlainObject(Object.create(null));

// Existing behavior unchanged
isPlainObject({});           // true
isPlainObject([]);           // false
isPlainObject(null);         // false
isPlainObject(new Date());   // false
```

Reviewed By: zeyap

Differential Revision: D88754908

Pulled By: javache

fbshipit-source-id: ea48908493b72da67699e48b35a6dc7e6714006d

Author: maman

packages/react-native/Libraries/Animated/nodes/AnimatedObject.js

@@ -24,12 +24,17 @@ export function isPlainObject(
   /* $FlowFixMe[incompatible-type-guard] - Flow does not know that the prototype
      and ReactElement checks preserve the type refinement of `value`. */
 ): value is $ReadOnly<{[string]: mixed}> {
+  const proto =
+    value !== null && typeof value === 'object'
+      ? Object.getPrototypeOf(value)
+      : undefined;
+  if (proto === undefined) {
+    // $FlowFixMe[incompatible-type-guard]
+    return false;
+  }
   return (
     // $FlowFixMe[incompatible-type-guard]
-    value !== null &&
-    typeof value === 'object' &&
-    Object.getPrototypeOf(value).isPrototypeOf(Object) &&
-    !isValidElement(value)
+    (proto == null || proto.isPrototypeOf(Object)) && !isValidElement(value)
   );
 }