Only attempt stopping PluginManagers looping call if it's running.

deluge/component.py

@@ -172,7 +172,8 @@ class ComponentRegistry:
             try:
                 self.components[component].shutdown()
             except Exception, e:
-                log.debug("Unable to call shutdown(): %s", e)
+                log.debug("Unable to call shutdown()")
+                log.exception(e)
 
 
 _ComponentRegistry = ComponentRegistry()

deluge/core/pluginmanager.py

@@ -65,6 +65,7 @@ class PluginManager(deluge.pluginmanagerbase.PluginManagerBase,
         # Disable all enabled plugins
         self.disable_plugins()
         # Stop the update timer
+        if self.update_timer.running:
             self.update_timer.stop()
 
     def shutdown(self):