increment correct supplier

Author: nhsd-david-wass

lambdas/supplier-allocator/src/handler/allocate-handler.ts

@@ -311,7 +311,7 @@ export default function createSupplierAllocatorHandler(deps: Deps): SQSHandler {
         incrementAllocation(
           volumeGroupAllocations,
           supplierDetails?.volumeGroupId ?? "unknown",
-          supplierSpec.supplierId,
+          supplierDetails?.supplierSpec?.supplierId ?? "unknown",
           1,
           deps,
         );