Avoid running change handlers on config.clear

qutebrowser/config/config.py

@@ -415,8 +415,9 @@ class Config(QObject):
         file.
         """
         for name, values in self._values.items():
-            values.clear()
-            self.changed.emit(name)
+            cleared = values.clear()
+            if cleared:
+                self.changed.emit(name)
 
         if save_yaml:
             self._yaml.clear()

qutebrowser/config/configutils.py

@@ -92,7 +92,9 @@ class Values:
 
     def clear(self):
         """Clear all customization for this value."""
+        had_values = bool(self._values)
         self._values = []
+        return had_values
 
     def _get_fallback(self):
         """Get the fallback global/default value."""