if (!session_id()) session_start();
is not a bug.
It is in place to work around a problem in PHP where the session contents are not available on page load, it should not cause a MySQL Error.
Perhaps it would help us debug the problem if you could provide the exact text of the Error, I dont believe it would have been the same as the origianl error you reported if you had renamed the column.
Along with the error, it would help if you could compress a copy of the resume_Detail.php page before it was changed into a zip file and attach it to your replay so we could the code generating the error.