Method reponsible for creating a token of given values is not meant to be
used with empty optionals. Thus, having requested a token of the columns
containing null values resulted with an exception being thrown. This kind
of behaviour was not compatible with the one applied in cassandra.
To fix this, before the computation of a token, it is checked whether
no null value is contained. If any value in the processed vector is null,
null value is returned.
Fixes: #10594Closes#10942
bf34589fc1