fix distribution combo

GUI/View/Instrument/DistributionSelector.cpp

@@ -40,7 +40,7 @@ DistributionSelector::DistributionSelector(std::optional<MeanConfig> mean_config
             createDistributionWidgets();
             emit distributionChanged();
         },
-        false);
+        true);
     m_distributionCombo->setEnabled(allow_distr);
     m_formLayout->addRow("Distribution:", m_distributionCombo);