Fix issue #251 and others 'undefined array key' errors.

[nerun]

This is a diff between my changes and the file from current master branch. These lines were added. These additions are harmless to the plugin and has no reasons to not add them:

39a40,46
>         
>         if ( !isset($USERINFO['grps']) ){
>             $USERINFO['grps'] = '';
>         }
>         if ( !isset($INFO['id']) ){
>             $INFO['id'] = '';
>         }
72a80,82
>         if ( !isset($JSINFO['move_renameokay']) ){
>             $JSINFO['move_renameokay'] = '';
>         }

Issue #251