kivy: fix "use change addresses" setting (previously ignored, always on)

this config setting is stored in the WalletStorage unlike most others

closes #5643

electrum/gui/kivy/main_window.py

@@ -159,7 +159,10 @@ class ElectrumWindow(App):
 
     use_change = BooleanProperty(False)
     def on_use_change(self, instance, x):
-        self.electrum_config.set_key('use_change', self.use_change, True)
+        if self.wallet:
+            self.wallet.use_change = self.use_change
+            self.wallet.storage.put('use_change', self.use_change)
+            self.wallet.storage.write()
 
     use_unconfirmed = BooleanProperty(False)
     def on_use_unconfirmed(self, instance, x):
@@ -339,7 +342,6 @@ class ElectrumWindow(App):
         self.fx = self.daemon.fx
 
         self.use_rbf = config.get('use_rbf', True)
-        self.use_change = config.get('use_change', True)
         self.use_unconfirmed = not config.get('confirmed_only', False)
 
         # create triggers so as to minimize updating a max of 2 times a sec
@@ -783,7 +785,7 @@ class ElectrumWindow(App):
             self._trigger_update_wallet()
 
     @profiler
-    def load_wallet(self, wallet):
+    def load_wallet(self, wallet: 'Abstract_Wallet'):
         if self.wallet:
             self.stop_wallet()
         self.wallet = wallet
@@ -800,6 +802,8 @@ class ElectrumWindow(App):
         except InternalAddressCorruption as e:
             self.show_error(str(e))
             send_exception_to_crash_reporter(e)
+            return
+        self.use_change = self.wallet.use_change
 
     def update_status(self, *dt):
         if not self.wallet: