Andy what's mean this error ???

GT::Plugins (7636): Error running plugin PRE hook: Plugins::Edit_Case::add_link. Reason: Plugins::Edit_Case::add_link does not exist in Plugins/Edit_Case at /home/public_html/cgi-bin/admin/Links/Table/Links.pm line 88.

Stack Trace
======================================
Links (7636): Links::environment called at /home/public_html/cgi-bin/admin/Links.pm line 524 with no arguments.
Links (7636): Links::fatal called at GT::Base::error line 381 with arguments
(GT::Plugins (7636): Error running plugin PRE hook: Plugins::Edit_Case::add_link. Reason: Plugins::Edit_Case::add_link does not exist in Plugins/Edit_Case at /home/public_html/cgi-bin/admin/Links/Table/Links.pm line 88.
).
Links (7636): GT::Base::error called at GT::Plugins::_load_hook line 277 with arguments
(GT::Plugins=HASH(0x8498c24), PLUGINERR, FATAL, PRE, Plugins::Edit_Case::add_link, Plugins::Edit_Case::add_link does not exist in Plugins/Edit_Case).
Links (7636): GT::Plugins::_load_hook called at /home/public_html/cgi-bin/admin/GT/Plugins.pm line 98 with arguments
(GT::Plugins=HASH(0x8498c24), Plugins::Edit_Case::add_link, PRE).
Links (7636): GT::Plugins::dispatch called at /home/public_html/cgi-bin/admin/Links/Table/Links.pm line 88 with arguments
(GT::Plugins, /home/public_html/cgi-bin/admin/Plugins, add_link, CODE(0x848ba18), HASH(0x83b5ff8)).
Links (7636): Links::Table::Links::add called at GT::SQL::Admin::add_record line 456 with arguments
(Links::Table::Links=HASH(0x8411038), HASH(0x83b5ff8)).
Links (7636): GT::SQL::Admin::add_record called at /home/public_html/cgi-bin/admin/GT/SQL/Admin.pm line 121 with arguments
(Links::Admin=HASH(0x8407204)).
Links (7636): GT::SQL::Admin::process called at admin.cgi line 77 with arguments
(Links::Admin=HASH(0x8407204), db, GT::SQL=HASH(0x82dd48c), cgi, GT::CGI=HASH(0x82d3bb0)).
Links (7636): main::db_request called at admin.cgi line 55 with no arguments.
Links (7636): main::main called at admin.cgi line 23 with no arguments.

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Thanks in Advance
Bye From Italy