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

Browser.py

@@ -53,6 +53,7 @@ class Browser(ft.Row):
         OnPathChanged: Optional[Callable[[Path], None]] = None,
         OnBookmarksChanged: Optional[Callable[[], None]] = None,
         OnSidebarSettingsChanged: Optional[Callable[[], None]] = None,
+        OnToggleSidebar: Optional[Callable[[], None]] = None,
         EntryFilter: Optional[Callable[[Path], bool]] = None,
         OnActivateFile: Optional[Callable[[Path], None]] = None,
         OnSelectionChanged: Optional[Callable[[], None]] = None,
@@ -64,6 +65,7 @@ class Browser(ft.Row):
         self.OnPathChanged = OnPathChanged
         self.OnBookmarksChanged = OnBookmarksChanged
         self.OnSidebarSettingsChanged = OnSidebarSettingsChanged
+        self.OnToggleSidebar = OnToggleSidebar  # Ctrl+B; the sidebar lives in Main.py, not here
         # Hooks for picker mode (Picker.py), all unused in the normal window:
         # which entries to list, what double-click/Enter on a file does
         # (instead of xdg-open), and what Escape does.
@@ -360,7 +362,7 @@ class Browser(ft.Row):
         self._Refresh()
         if self.Config.ShowPreview:
             self.PreviewPane.ShowPath(None)
-        if self.Config.ShowTags:
+        if self._TagsShown():
             self.TagPanel.ShowPath(None)
         if self.OnPathChanged:
             self.OnPathChanged(TargetPath)
@@ -468,9 +470,16 @@ class Browser(ft.Row):
         ShowPath = self.SelectedPath if len(self.SelectedPaths) <= 1 else None
         if self.Config.ShowPreview:
             self.PreviewPane.ShowPath(ShowPath)
-        if self.Config.ShowTags:
+        if self._TagsShown():
             self.TagPanel.ShowPath(ShowPath)
 
+    def _TagsShown(self) -> bool:
+        """Whether the tags panel is actually in the window. Tags placed
+        "under_preview" live in the preview column, so hiding the preview
+        (Ctrl+P) hides them too even with ShowTags on; updating the panel then
+        crashed with "TagPanel must be added to the page first"."""
+        return self.Config.ShowTags and (self.Config.TagsPosition != "under_preview" or self.Config.ShowPreview)
+
     def _TargetSelection(self, Entry: Path) -> list[Path]:
         """What a right-click/menu action on Entry should operate on: the
         whole live selection if Entry is part of a multi-selection, otherwise
@@ -747,8 +756,11 @@ class Browser(ft.Row):
             self.GoForward()
         elif Event.key == "A" and Event.ctrl:
             self._SelectAll()
-        elif Event.key == "B" and Event.ctrl:
+        elif Event.key == "B" and Event.ctrl and Event.shift:
             self._ToggleBreadcrumbs()
+        elif Event.key == "B" and Event.ctrl:
+            if self.OnToggleSidebar:
+                self.OnToggleSidebar()
         elif Event.key == "P" and Event.ctrl:
             self._TogglePreview()
         elif Event.key == "H" and Event.ctrl: