setWritingSystem gives "out of range" error

Hi, I'm having problem when I try to add a filter.

I have a QDialog which controls the font of a text, it has a QFontComboBox for the family, a QComboBox for the size and another for the writingSystem.

I want to change the QFontComboBox, appling a filter, depending of which writingSystem is selected.

It's a pretty clear code, and it gives an strage "out of range" problem when I execute.

Code:

---

void CFontsDialog::combBWritSystemsChanged( QString strWrtSystems )
{//strWrtSystems is the selected writingSystem in the comboBox
	QFontDatabase::WritingSystem auxWrSystem = ui.m_combBFamilies->writingSystem();
 
	QFontDatabase database;
	QList<QFontDatabase::WritingSystem> lWrSys = database.writingSystems(); 
    for(int i = 0; i < lWrSys.size(); ++i)
	{
		if(QFontDatabase::writingSystemName(lWrSys.at(i)) == strWrtSystems)
		{
            auxWrSystem = lWrSys.at(i); //this line is always executed, the variable is valid
			break;
		}
	}
	ui.m_combBFamilies->setWritingSystem(auxWrSystem); //error, but the variable seems right :S
}

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any clue? thanks!