Do not join SSID if SSID string is empty on start

Fixes an issue where the board would attempt to join wifi AP on start
even if there was no wifi ssid set in the zuluscsi.ini file.

Co-authored-by: joshua stein <jcs@jcs.org>

src/ZuluSCSI.cpp

@@ -843,7 +843,8 @@ static void reinitSCSI()
   if (scsiDiskCheckAnyNetworkDevicesConfigured())
   {
     platform_network_init(scsiDev.boardCfg.wifiMACAddress);
-    platform_network_wifi_join(scsiDev.boardCfg.wifiSSID, scsiDev.boardCfg.wifiPassword);
+    if (scsiDev.boardCfg.wifiSSID[0] != '\0')
+      platform_network_wifi_join(scsiDev.boardCfg.wifiSSID, scsiDev.boardCfg.wifiPassword);
   }
 #endif // ZULUSCSI_NETWORK