settings: rollback value on save error

src/settings/setting/base.py

@@ -250,6 +250,7 @@ class BaseSetting:
         return self._current_value if self._current_value is not None else self.default
 
     def _set_backend_value(self, value):
+        previous_value = self._current_value
         self._current_value = value
         self._update_widget()
         self._set_busy(True)
@@ -261,6 +262,8 @@ class BaseSetting:
             if self._destroyed:
                 return
             self.logger.error(f"Value save failed for {self.name}: {exc}")
+            self._current_value = previous_value
+            self._update_widget()
 
         def _on_done():
             if self._destroyed: