Notice: Trying to get property 'num_rows' of non-object (File: DataBase.php, Line: 162)

  Trace:
#0 /var/www/vhosts/pentawar.net/db.pentawar.net/common/classes/DataBase.php(162): ErrorHandler->handler()
#1 /var/www/vhosts/pentawar.net/db.pentawar.net/scripts/functions.php(426): DataBase->num_rows()
#2 /var/www/vhosts/pentawar.net/db.pentawar.net/scripts/func.skills.php(78): getClassData()
#3 /var/www/vhosts/pentawar.net/db.pentawar.net/index.php(39): require_once('/var/www/vhosts...')
#4 {main}