message: billing - safe billing of "ghost"  sessions
diff: @@ -64,6 +64,10 @@ export default class PricingEngine {
  }
  public static extractFinalPricingData(pricingModel: ResolvedPricingModel): PricedConsumptionData[] {
  + if (!pricingModel) {
  + // Happens only when billing "ghost" sessions that were created with the former "Simple Pricing" module
  + return [];
  + }
  // Iterate throw the list of pricing definitions
  const pricedData: PricedConsumptionData[] = pricingModel.pricingDefinitions.map((pricingDefinition) =>
  PricingEngine.extractFinalPricedConsumptionData(pricingDefinition)
  