Handle 0-length domain names in Advapi32Util#getAccountBySid

[dbwiddis]

In rare/transient situations, such as UAC elevation or other SYSTEM account situations, the domain name can be an empty string. In this case cchDomainName is set to 0 and a zero-length array causes the function call to fail with an incorrect parameter. See oshi/oshi#1551 and oshi/oshi#637 for examples of failure symptoms.

Rather than adding code to handle the special case, we can simplify the code to avoid the initial call to get length, and prevent this error by using the max possible string lengths.

GetUserName docs indicate:

A buffer size of (UNLEN + 1) characters will hold the maximum length user name including the terminating null character. UNLEN is defined in Lmcons.h.

UNLEN is 256. The max local domain length (DNLEN) is 15, but to be conservative I used the max FQDN length of 255.

[dbwiddis]

This sample code from MSDN does a single call using MAX_NAME of 256 for both fields (which apparently works without null terminator because it's a fixed length array). One potential needed change is to test for the zero-length domain name when building the fqn field. It's not clear from the docs that the length parameter is reset when the function doesn't fail.

[matthiasblaesing]

Looks good to me.