Fixed null error in plugin opts and added a test for it (#9945)

* Fixed null error in plugin opts and added a test for it

* Remove !opts and add opts === null check to avoid confusion with false and undefined cases

Co-Authored-By: divbhasin <divbest99@gmail.com>

packages/babel-core/src/config/validation/option-assertions.js

@@ -337,7 +337,7 @@ function assertPluginItem(loc: GeneralPath, value: mixed): PluginItem {
       if (
         opts !== undefined &&
         opts !== false &&
-        (typeof opts !== "object" || Array.isArray(opts))
+        (typeof opts !== "object" || Array.isArray(opts) || opts === null)
       ) {
         throw new Error(
           `${msg(access(loc, 1))} must be an object, false, or undefined`,