fix compiler warning

Author: matth-x

src/MicroOcpp/Model/Transactions/TransactionService.cpp

@@ -47,6 +47,10 @@ TransactionService::Evse::Evse(Context& context, TransactionService& txService,
     transaction = txStore.loadTransaction(txNrLatest); //returns nullptr if txNrLatest does not exist on flash
 }
 
+TransactionService::Evse::~Evse() {
+    
+}
+
 bool TransactionService::Evse::beginTransaction() {
 
     if (transaction) {

src/MicroOcpp/Model/Transactions/TransactionService.h

@@ -66,6 +66,7 @@ class TransactionService : public MemoryManaged {
 
     public:
         Evse(Context& context, TransactionService& txService, Ocpp201::TransactionStoreEvse& txStore, unsigned int evseId);
+        virtual ~Evse();
 
         void loop();