Update generic.class.php

Fixed a bug, when using GetTagValue(), and specifying an element that does not exist, the function would  would return a warning:
Notice: Undefined offset: 1 in /etc/zpanel/panel/dryden/ws/generic.class.php

$matches does not initialized first when being passed into preg_match.
trinary used for return statement.  If found, return it, else null.
Removed redundant php close tag.