Stricter SQL checks (#2829)

* Add assert(false) on unexpected mysql error

* Only allow one transaction at the same time

src/shared/Database/Database.cpp

@@ -487,9 +487,7 @@ bool Database::CommitTransaction()
         return false;
 
     //check if we have pending transaction
-    //ASSERT(m_TransStorage->get());
-    if (!m_TransStorage->get())
-        return false;
+    ASSERT(m_TransStorage->get()); // if we will get a nested transaction request - we MUST fix code!!!
 
     //if async execution is not available
     if(!m_bAllowAsyncTransactions)

src/shared/Database/DatabaseMysql.cpp

@@ -189,6 +189,7 @@ bool MySQLConnection::HandleMySQLError(uint32 errNo)
             return false;
         default:
             sLog.Out(LOG_DBERROR, LOG_LVL_MINIMAL, "Unhandled MySQL errno %u. Unexpected behaviour possible.", errNo);
+            ASSERT(false);
             return false;
     }
 }