Whenever I save new entry I get the following error message. But the entry is saved. I can open the entry and etdit it. When I save the edited version no error occurs. What does this error message mean and what can I do to fix it? I started with uninstalling the checkbox fieldtype, since I don´t need it, but this didn´t help. This error is not channel or custom fieldgroup specific. It comes up for all 3 channels that I have.
A PHP Error was encountered
Severity: Notice
Message: Undefined index: field_id_sitemap__ping_sitemap
Filename: checkboxes/ft.checkboxes.php
Line Number: 80
A PHP Error was encountered
Severity: Warning
Message: Invalid argument supplied for foreach()
Filename: checkboxes/ft.checkboxes.php
Line Number: 80
A PHP Error was encountered
Severity: Warning
Message: Cannot modify header information - headers already sent by (output started at /home/www/deleted_my_path-here/codeigniter/system/core/Exceptions.php:170)
Filename: libraries/Functions.php
Line Number: 809