Fix tags crash with preview hidden; Ctrl+B toggles the sidebar

Devices.py

@@ -165,14 +165,24 @@ class DevicesPanel(ft.Container):
         self.DeviceTiles: dict[str, ft.ListTile] = {}
         self.RefreshScheduled = False
         self.Busy: set[str] = set()  # devices being mounted/ejected right now
+        self.Unmounted = False
 
         self.List = ft.ListView(spacing=0)
         self.List.controls = self._BuildTiles()
         super().__init__(content=self.List, padding=0)
 
     def did_mount(self) -> None:
+        self.Unmounted = False
         self.page.run_task(self._Start)
 
+    def will_unmount(self) -> None:
+        # The sidebar gets rebuilt when its settings change; close this panel's
+        # D-Bus connection so old panels don't pile up listening to udisks2.
+        self.Unmounted = True
+        if self.Client is not None:
+            self.Client.Bus.disconnect()
+            self.Client = None
+
     async def _Start(self) -> None:
         try:
             self.Client = await UDisksClient.Connect()
@@ -184,20 +194,21 @@ class DevicesPanel(ft.Container):
         await self._Refresh(IsStartup=True)
 
     async def _PollLoop(self) -> None:
-        while True:
+        while not self.Unmounted:
             self._Show(ListFallbackDevices())
             await asyncio.sleep(PollInterval)
 
     def _ScheduleRefresh(self) -> None:
         # One plug-in fires a burst of signals; refresh once per burst.
-        if not self.RefreshScheduled:
+        if not self.RefreshScheduled and not self.Unmounted:
             self.RefreshScheduled = True
             self.page.run_task(self._DelayedRefresh)
 
     async def _DelayedRefresh(self) -> None:
         await asyncio.sleep(0.25)
         self.RefreshScheduled = False
-        await self._Refresh()
+        if self.Client is not None and not self.Unmounted:
+            await self._Refresh()
 
     async def _Refresh(self, IsStartup: bool = False) -> None:
         try: