fail cleanly when a printer does not answer GS I 1

Claude-Session: https://claude.ai/code/session_01E6N3P4nSZLtp4BC2LXVref

Inspectron.Epson/PrintServer/PrintServices/EpsonPrintService.cs

@@ -39,6 +39,14 @@ public class EpsonPrintService: IPrintService
 
             _logger.LogInformation("Printer ID({ip}): {PrinterId}", printerIp, printerId);
 
+            if (printerId is null)
+            {
+                _logger.LogWarning(
+                    "Printer {PrinterIp} did not answer GS I 1, so its model is unknown; " +
+                    "cannot choose a printer adapter", printerIp);
+                return PrintResult.Fail(PrintErrorType.Other);
+            }
+
             var status = await epsonPrinter.GetPrinterStatusAsync();
             if (!status.IsOnline)
             {