compat/winansi: check result before using Name field

NtQueryObject can return a success but fill out no name.
In those situations, it will set the last argument to the size of the
passed in struct, that being 16, to indicate that the name field is NULL.

Without this change, using git compiled for Windows under wine in certain
circumstances can result in a crash due to a null pointer dereference.

Signed-off-by: Christopher Degawa <[email protected]>

Author: 1480c1

compat/winansi.c

@@ -573,6 +573,8 @@ static void detect_msys_tty(int fd)
 	if (!NT_SUCCESS(NtQueryObject(h, ObjectNameInformation,
 			buffer, sizeof(buffer) - 2, &result)))
 		return;
+	if (result <= sizeof(*nameinfo))
+		return;
 	name = nameinfo->Name.Buffer;
 	name[nameinfo->Name.Length / sizeof(*name)] = 0;