Remove empty charge period guard clause

With [Exclude ended licences in two-part tariff matching](#595) being merged we should always have a populated charge period so there is no need for the guard clause any more.

app/services/check/stand-ins.service.js

@@ -182,20 +182,11 @@ async function _prepareLicencesForAllocation (licences, billingPeriod) {
       _sortChargeReferencesBySubsistenceCharge(chargeReferences)
       chargeVersion.chargePeriod = DetermineChargePeriodService.go(chargeVersion, billingPeriod)
 
-      // NOTE: Imagine the scenario where a billing account change is due to happen. The users will create a new charge
-      // version whose start date will be when the account is due to change, for example 1 Oct. So, the charge version
-      // we are looking at has a `startDate:` of 2023-10-01. But then someone marks the licence as revoked in NALD on
-      // 2023-08-01. In this scenario DetermineChargePeriodService will return an empty charge period because it will
-      // have calculated the charge period start date as 2023-10-01 and the end date as 2023-08-01. Clearly, this is
-      // incompatible so the service actually returns `{ startDate: null, endDate: null }`. This check is to handle
-      // scenarios like this
-      if (chargeVersion.chargePeriod.startDate) {
-        chargeReferences.forEach((chargeReference) => {
-          const { chargeElements } = chargeReference
-
-          _prepChargeElementsForMatching(chargeElements, chargeVersion.chargePeriod)
-        })
-      }
+      chargeReferences.forEach((chargeReference) => {
+        const { chargeElements } = chargeReference
+
+        _prepChargeElementsForMatching(chargeElements, chargeVersion.chargePeriod)
+      })
     })
   }
 }