win32: check for NULL after creating thread

Check for NULL handles, not "INVALID_HANDLE,"
as CreateThread guarantees a valid handle in most cases.

The return value for failed thread creation is NULL,
not INVALID_HANDLE_VALUE, unlike other Windows
API functions.

Signed-off-by: Seija Kijin <doremylover123@gmail.com>

compat/winansi.c

@@ -644,7 +644,7 @@ void winansi_init(void)
 
 	/* start console spool thread on the pipe's read end */
 	hthread = CreateThread(NULL, 0, console_thread, NULL, 0, NULL);
-	if (hthread == INVALID_HANDLE_VALUE)
+	if (!hthread)
 		die_lasterr("CreateThread(console_thread) failed");
 
 	/* schedule cleanup routine */