Don't let the "send from list" sort itself

Order matters for correspondence of display position to internal list.
Fixes #1420.

gui/qt/main_window.py

@@ -1017,6 +1017,7 @@ class ElectrumWindow(QMainWindow):
         self.from_label = QLabel(_('From'))
         grid.addWidget(self.from_label, 3, 0)
         self.from_list = MyTreeWidget(self, self.from_list_menu, ['',''])
+        self.from_list.setSortingEnabled(False)
         self.from_list.setHeaderHidden(True)
         self.from_list.setMaximumHeight(80)
         grid.addWidget(self.from_list, 3, 1, 1, 3)