minor fix for settings dialog combo

lib/gui_qt.py

@@ -1297,7 +1297,9 @@ class ElectrumWindow(QMainWindow):
         grid.addWidget(gui_label , 7, 0)
         gui_combo = QComboBox()
         gui_combo.addItems(['Lite', 'Classic', 'Gtk', 'Text'])
-        gui_combo.setCurrentIndex(gui_combo.findText(self.config.get("gui","classic").capitalize()))
+        index = gui_combo.findText(self.config.get("gui","classic").capitalize())
+        if index==-1: index = 1
+        gui_combo.setCurrentIndex(index)
         grid.addWidget(gui_combo, 7, 1)
         grid.addWidget(HelpButton(_('Select which GUI mode to use at start up. ')), 7, 2)
         if not self.config.is_modifiable('gui'):