ext4: Return the PTR_ERR of the correct pointer in setup_new_group_blocks()

(cherry picked from commit c09eef30

)

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andy Whitcroft <apw@canonical.com>