Fix data() with long datatype for Mimer SQL

Calling data() for parameters of the type bigint
failed in combination with stored procedures with
output parameters. Cast the result to qlonglong to
fix it.

Pick-to: 6.6
Change-Id: I84ef04ed26821b92ef7c5bcdf12b778e91450e0b
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
(cherry picked from commit ad84754b5888971074a44ec698d20a32aebeec14)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/plugins/sqldrivers/mimer/qsql_mimer.cpp

@@ -690,7 +690,7 @@ QVariant QMimerSQLResult::data(int i)
                                         err, QSqlError::StatementError, d->drv_d_func()));
                 return QVariant(QMetaType(type), nullptr);
             }
-            return QString::number(resLongLong).toLongLong();
+            return (qlonglong)resLongLong;
         }
         case MimerColumnTypes::Boolean: {
             err = MimerGetBoolean(d->statementhandle, static_cast<std::int16_t>(i) + 1);