ReferenceError: doc is not defined. Firebase Functions Node.js JavaScript

Can anyone help me solve this issue? I am using Firebase Functions node.js javascript. The first code is working perfectly while the second is showing "ReferenceError: doc is not defined". The only difference between these two codes is that the second one is inside the if clause. Please help.

Code One - Works Perfectly:

const usersRef = admin.firestore().collection('users');

const snapshot = await usersRef
  .where('gender', '==', 'Male')
  .where('account_live', '==', true)
  .where('account_suspended', '==', false)
  .get();
if (snapshot.empty) {
  console.log('No matching documents.');
  return;
}
snapshot.forEach(async (doc) => {
  console.log(doc.id, '=>', doc.data());
  var uid = doc.get('uid');
  await washingtonRef.update({
    global: admin.firestore.FieldValue.arrayUnion(
      'sorting_inside_update_successfull ' + uid
    ),
  });
});

Code Two - Not Working:

var docBefore = change.before;
var docAfter = change.after;

const global_list = docAfter.get('global').length;
console.log('GLOBAL ARRAY SIZE .' + global_list);
if (global_list < 50) {
  const usersRef = admin.firestore().collection('users');

  const snapshot = await usersRef
    .where('gender', '==', 'Male')
    .where('account_live', '==', true)
    .where('account_suspended', '==', false)
    .get();
  if (snapshot.empty) {
    console.log('No matching documents.');
    return;
  }
  snapshot.forEach(async (doc) => {
    console.log(doc.id, '=>', doc.data());
    var uid = doc.get('uid');
    console.log('USER_UID_INSIDE : ' + user_uid);
    const updateRef = admin
      .firestore()
      .collection('query_sorted')
      .doc(user_uid);
    await updateRef.update({
      global: admin.firestore.FieldValue.arrayUnion(
        'sorting_inside_successfull ' + uid
      ),
    });
  });
} else {
  return null;
}

Please Help.