message: Handle NPE in Charging Station REST call
diff: @@ -3,6 +3,7 @@ import { OCPPChangeAvailabilityCommandParam, OCPPChangeAvailabilityCommandResult
  import { OCPPIncomingRequest, OCPPMessageType, OCPPOutgoingRequest } from '../../../types/ocpp/OCPPCommon';
  import { ServerAction, WSServerProtocol } from '../../../types/Server';
  +import BackendError from '../../../exception/BackendError';
  import ChargingStationClient from '../ChargingStationClient';
  import Configuration from '../../../utils/Configuration';
  import Logging from '../../../utils/Logging';
  @@ -23,7 +24,16 @@ export default class JsonRestChargingStationClient extends ChargingStationClient
  super();
  this.tenantID = tenantID;
  // Get URL
  - let chargingStationURL: string = chargingStation.chargingStationURL;
  + let chargingStationURL = chargingStation.chargingStationURL;
  + if (!chargingStationURL) {
  + throw new BackendError({
  + source: chargingStation.id,
  + module: MODULE_NAME,
  + method: 'constructor',
  + message: 'Cannot access the Charging Station via a REST call because no URL is provided',
  + detailedMessages: { chargingStation }
  + });
  + }
  // Check URL: remove starting and trailing '/'
  if (chargingStationURL.endsWith('/')) {
  // Remove '/'
  @@ -140,7 +150,8 @@ export default class JsonRestChargingStationClient extends ChargingStationClient
  source: this.chargingStation.id,
  action: ServerAction.WS_REST_CLIENT_CONNECTION_CLOSED,
  module: MODULE_NAME, method: 'onClose',
  - message: `Connection closed to '${this.serverURL}', Message: '${Utils.getWebSocketCloseEventStatusString(code)}', Code: '${code}'`
  + message: `Connection closed to '${this.serverURL}', Message: '${Utils.getWebSocketCloseEventStatusString(code)}', Code: '${code}'`,
  + detailedMessages: { code }
  });
  };
  // Handle Error Message
  