Category tree of uploaded documents

archerleonard wrote on Thursday, August 07, 2014:

The commit is about that the root of category tree of uploaded documents doesn’t start from 1.
If the root doesn’t start from 1, you will get null from “$this->_id_name[$parent]” and then the application will fail before finding “$parent!=0”.
So I contributed my code. No matter what the root of category tree starts from,
it will be okay.

Comments and code review are welcomed.
Thanks a million.