I just updated my ctools module from a 7.x.1.0-alpha3 to a 7.x.1.0 and a notice occured when i visit an administrive page provided by the module panels. This notice is from the page_manager feature of ctools in the line 157 of the file page_manager.admin.inc.
Some paths saved in $task['admin path'] ended by a '/', that's why the last result of the explode is an empty string. The test $bit != '!' occured an error in this case.
Please find in attachment a simplistic patch to solve this notice.