Initialize time zone variable (zone)

As found and reported by Talisam author, apam (HAPPYLND).

sscanf() won't initialize the buffer of the argument passed if the format string is not matched, so when there was no hexadecimal/SMB timezone value, the timezone specified in the ISO date/time string (if any) would be overwritten with 0, converted from the uninitialized 'zone' variable (unlikely to be valid hex-ASCII chars). Thanks apam!