only apply convert() function if either source or target charsets are non trivial (no need for convert if both are trivial)
only apply convert() function if either source or target charsets are non trivial (no need for convert if both are trivial)

Signed-off-by: Shlomi Noach <f07557902aa82e6b2846c90bd293a06970411e12@users.noreply.github.com>

vitessio/vitess,vitessio/vitess,vitessio/vitess,mahak/vitess,mahak/vitess,vitessio/vitess,mahak/vitess,mahak/vitess,vitessio/vitess,mahak/vitess,mahak/vitess,vitessio/vitess,mahak/vitess,vitessio/vitess,mahak/vitess,vitessio/vitess