no users are listed on the share page. in Moodle versions 1.9.4 >> 1.9.9
since sql query is using old and deprecated tables.

to fix, open file file_manager/print_lib.php and change the lines:

$sqltoexecute = "SELECT {$CFG->prefix}user.id, {$CFG->prefix}user.firstname, {$CFG->prefix}user.lastname, {$CFG->prefix}role.name
FROM {$CFG->prefix}user, {$CFG->prefix}course_display, {$CFG->prefix}role_assignments, {$CFG->prefix}role
WHERE (course = $id AND {$CFG->prefix}course_display.userid = {$CFG->prefix}user.id
AND {$CFG->prefix}user.id = {$CFG->prefix}role_assignments.userid
AND {$CFG->prefix}role_assignments.roleid = {$CFG->prefix}role.id)";

(better, turn them into comments)

to:
$sqltoexecute = "SELECT u.id, u.firstname, u.lastname, r.name
FROM {$CFG->prefix}user u
JOIN {$CFG->prefix}role_assignments ra ON ra.userid = u.id
JOIN {$CFG->prefix}role r ON ra.roleid = r.id
JOIN {$CFG->prefix}context con ON ra.contextid = con.id
JOIN {$CFG->prefix}course c ON c.id = con.instanceid AND con.contextlevel = 50
WHERE r.shortname = 'student' AND c.id = {$id}";

enjoy