Don't assume USB device is configured when looking for endpoints

[binaryf0x]

If the USB device is unconfigured then USBDevice.configuration will be null. The full USBDevice.configurations array should be used instead. After opening the device the correct configuration is selected.

[Cellivar]

Nice, thank you!

[github-actions]

➿ Code coverage

Filename	Statements	Branches	Functions	Lines
src/Documents/BitmapGRF.ts	66.47%	57.41%	72.73%	64.38%
src/WebZlpError.ts	33.33%	100%	50%	33.33%
src/index.ts	100%	100%	100%	100%
src/Documents/Commands.ts	25.84%	41.94%	9.17%	9.58%
src/Printers/Configuration/PrinterOptions.ts	25.64%	66.67%	6.25%	12.12%
src/Printers/Models/PrinterModel.ts	39.02%	18.18%	11.11%	13.79%
src/Printers/Configuration/SerialPortSettings.ts	97.06%	100%	85.71%	85.71%
src/Printers/Configuration/MediaOptions.ts	69.23%	33.33%	62.5%	20%
src/Documents/ConfigDocument.ts	28.21%	0%	28.57%	28.21%
src/Documents/Document.ts	40.91%	0%	33.33%	45%
src/Documents/LabelDocument.ts	44.83%	60%	26.32%	38.46%
src/Documents/ReadyToPrintDocuments.ts	27.27%	100%	0%	22.22%
src/Printers/Communication/LineBreakTransformer.ts	0%	100%	0%	0%
src/Printers/Communication/PrinterCommunication.ts	76.92%	50%	50%	50%
src/Printers/Communication/UsbPrinterDeviceChannel.ts	4.11%	0%	0%	4.11%
src/Printers/Languages/EplPrinterCommandSet.ts	12.07%	12.86%	11.11%	12.57%
src/Printers/Models/PrinterModelDb.ts	10%	0%	0%	10%
src/Printers/Models/EplPrinterModels.ts	11.76%	100%	0%	11.76%
src/Printers/Languages/PrinterCommandSet.ts	20.2%	6.25%	16.67%	19.15%
src/Printers/PrinterCommunicationOptions.ts	0%	100%	0%	0%
src/Printers/Printer.ts	11.46%	0%	0%	11.58%
src/Printers/Languages/ZplPrinterCommandSet.ts	3.18%	0%	0%	3.21%
src/PrinterUsbManager.ts	4.65%	0%	0%	4.88%