Merge pull request #604 from flowln/fix_crash_with_gtk2

fix: crash with GTK2 theme due to QProxyStyle in ManagedPackPage

launcher/ui/pages/instance/ManagedPackPage.cpp

@@ -7,6 +7,7 @@
 
 #include <QListView>
 #include <QProxyStyle>
+#include <QStyleFactory>
 
 #include <HoeDown.h>
 
@@ -60,6 +61,9 @@ ManagedPackPage::ManagedPackPage(BaseInstance* inst, InstanceWindow* instance_wi
 
     ui->setupUi(this);
 
+    // NOTE: GTK2 themes crash with the proxy style.
+    // This seems like an upstream bug, so there's not much else that can be done.
+    if (!QStyleFactory::keys().contains("gtk2"))
         ui->versionsComboBox->setStyle(new NoBigComboBoxStyle(ui->versionsComboBox->style()));
 
     ui->reloadButton->setVisible(false);