There's no use assigning the output of strtoul() to a 32-bit variable
then checking that against ULONG_MAX. Instead use a "unsigned long"
as the temporary variable. Also, only check against UID_MAX/GID_MAX;
these are both going to be smaller than ULONG_MAX on both 32- and 64-bit
platforms.
If the user deletes a field while editing (as an easy way of making
that field empty) then "save" for that field will not get initialized
before referencing it when constructing the new GECOS field.
