Core/PreparedStatements: Fixed a Coverity warning

src/server/shared/Database/PreparedStatement.cpp

@@ -446,7 +446,7 @@ std::string MySQLPreparedStatement::getQueryString(std::string const& sqlPattern
 
 //- Execution
 PreparedStatementTask::PreparedStatementTask(PreparedStatement* stmt, bool async) :
-m_stmt(stmt)
+m_stmt(stmt), m_result(nullptr)
 {
     m_has_result = async; // If it's async, then there's a result
     if (async)