manager: Handle removal of VM during on_shutdown.

Fixes QubesOS/qubes-issues#5105

qubesmanager/qube_manager.py

@@ -1061,7 +1061,7 @@ class VmManagerWindow(ui_qubemanager.Ui_VmManagerWindow, QMainWindow):
                             update(event="outdated")
             self.proxy.invalidate()
             self.table_selection_changed()
-        except exc.QubesDaemonAccessError:
+        except (exc.QubesDaemonAccessError, exc.QubesVMNotFoundError):
             return  # the VM was deleted before its status could be updated
         except KeyError:  # adding the VM failed for some reason
             self.on_domain_added(None, None, vm)