Bug 27526: Fix encoding issue on subfield

Bug 27526: Fix encoding issue on subfield

If you have a "é" subfield it should work!

Note that VARCHAR(1) for binary means 1-byte (from MySQL doc):
"For example, if the default character set is utf8mb4, CHAR(5) BINARY is
treated as CHAR(5) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin. This
differs from BINARY(5), which stores 5-byte binary strings that have the
binary character set and collation."

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>