BUG OF THE MONTH | Possible null dereference

public static void RemoveMarkAsNew(....)
{
  ....
  var listTags = tagDao.GetNewTags(userID, (Folder)fileEntry, true).ToList();
  valueNew = listTags.FirstOrDefault(tag => tag.EntryId.Equals(....)).Count;
  ....
}

V3146 Possible null dereference. The ‘listTags.FirstOrDefault’ can return default null value. FileMarker.cs 299

The analyzer detected unsafe use of the result of calling the FirstOrDefault method. This method returns the default value if there is no object in the list that matches the search predicate. The default value for reference types is an empty reference (null). Accordingly, before using the resulting reference, one must check it, and not call the property immediately, as opposed to as it is here.

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