Improve Database API to avoid memory leaks in the future, part 3.

This commit reworks SqlQueryHolder to return a unique_ptr instead of a
raw pointer to the query's result in its API.

It also fixes a memory leak in Player::_LoadForgottenSkills() because
the incoming query result was not deleted.

src/framework/Utilities/Callback.h

@@ -20,6 +20,7 @@
 #define MANGOS_CALLBACK_H
 
 #include <functional>
+#include <memory>
 
 /// ---------- QUERY CALLBACKS -----------
 
@@ -33,7 +34,7 @@ namespace MaNGOS
 
             virtual ~IQueryCallback() = default;
             virtual void Execute() = 0;
-            virtual void SetResult(QueryResult* queryResult) = 0;
+            virtual void SetResult(std::unique_ptr<QueryResult> queryResult) = 0;
     };
 
     class QueryCallback : public IQueryCallback
@@ -54,18 +55,18 @@ namespace MaNGOS
 
             void Execute() override
             {
-                m_Callback(m_QueryResult);
+                m_Callback(m_QueryResult.release());
             }
 
-            void SetResult(QueryResult* queryResult) override
+            void SetResult(std::unique_ptr<QueryResult> queryResult) override
             {
-                m_QueryResult = queryResult;
+                m_QueryResult = std::move(queryResult);
             }
 
         private:
 
             std::function<void(QueryResult*)> m_Callback;
-            QueryResult* m_QueryResult;
+            std::unique_ptr<QueryResult> m_QueryResult;
     };
 }
 

src/game/Entities/CharacterHandler.cpp

@@ -600,14 +600,13 @@ void WorldSession::HandlePlayerLogin(LoginQueryHolder* holder)
     SendOfflineNameQueryResponses();
 
     // QueryResult *result = CharacterDatabase.PQuery("SELECT guildid,rank FROM guild_member WHERE guid = '%u'",pCurrChar->GetGUIDLow());
-    QueryResult* resultGuild = holder->GetResult(PLAYER_LOGIN_QUERY_LOADGUILD);
+    auto resultGuild = holder->GetResult(PLAYER_LOGIN_QUERY_LOADGUILD);
 
     if (resultGuild)
     {
         Field* fields = resultGuild->Fetch();
         pCurrChar->SetInGuild(fields[0].GetUInt32());
         pCurrChar->SetRank(fields[1].GetUInt32());
-        delete resultGuild;
     }
     else if (pCurrChar->GetGuildId())                       // clear guild related fields in case wrong data about nonexistent membership
     {