An instance may be invalidated before we try to recycle it.
We perform this by setting its value to a nullopt.
This patch adds a check for it when calculating its size.
This behavior didn't cause issues before because the catch
clause below caught errors caused by calling value() on
a nullopt, even though it was intended for errors from
get_instance_size.
Signed-off-by: Wojciech Mitros <wojciech.mitros@scylladb.com>
Closes#11500
7effd4c53a