Fix #1009 enabling a plugin twice in the gtkui

Prevent plugins from being enabled more than once in pluginmanagerbase

deluge/pluginmanagerbase.py

@@ -122,6 +122,10 @@ class PluginManagerBase:
             log.warning("Cannot enable non-existant plugin %s", plugin_name)
             return
 
+        if plugin_name in self.plugins:
+            log.warning("Cannot enable already enabled plugin %s", plugin_name)
+            return
+
         plugin_name = plugin_name.replace(" ", "-")
         egg = self.pkg_env[plugin_name][0]
         egg.activate()

deluge/ui/gtkui/preferences.py

@@ -882,7 +882,6 @@ class Preferences(component.Component):
         self.plugin_liststore.set_value(row, 1, not value)
         if not value:
             client.core.enable_plugin(name)
-            component.get("PluginManager").enable_plugin(name)
         else:
             client.core.disable_plugin(name)
             component.get("PluginManager").disable_plugin(name)