Bug fix for multi-file zmodem-send using wildcards

If the first specified file in the list had a wildcard pattern, multiple
ZRQINIT (request init) frames would be sent (one for each file matching
the first list item file pattern).

This was just found via code review, not in the wild.

src/sbbs3/sexyz.c

@@ -972,7 +972,7 @@ static int send_files(char** fname, uint fnames)
 			        , mode & XMODEM ? 'X' : mode & YMODEM ? 'Y' : 'Z');
 
 			if (mode & ZMODEM)
-				success = zmodem_send_file(&zm, path, fp, /* ZRQINIT? */ fnum == 0, &startfile, &sent_bytes);
+				success = zmodem_send_file(&zm, path, fp, /* ZRQINIT? */ xm.sent_files == 0, &startfile, &sent_bytes);
 			else    /* X/YMODEM */
 				success = xmodem_send_file(&xm, path, fp, &startfile, &sent_bytes);