fix resetting AVForm resolution combobox index to get change signal always fired during init

src/widget/form/settings/avform.cpp

@@ -125,6 +125,8 @@ void AVForm::onResProbingFinished(QList<QSize> res)
 	bodyUI->videoModescomboBox->blockSignals(true);
     for (QSize r : res)
         bodyUI->videoModescomboBox->addItem(QString("%1x%2").arg(QString::number(r.width()),QString::number(r.height())), r);
+	//reset index, otherwise cameras with only one resolution won't get initialized
+    bodyUI->videoModescomboBox->setCurrentIndex(-1);
     bodyUI->videoModescomboBox->blockSignals(false);
 
     bodyUI->videoModescomboBox->setCurrentIndex(bodyUI->videoModescomboBox->count()-1);