trivial fixes

plugins/c9.ide.editors/editors.js

@@ -183,6 +183,8 @@ define(function(require, module, exports) {
         });
         plugin.on("unload", function(){
             loaded = false;
+            defaultEditor = null;
+            group = null;
         });
         
         /***** Register and define API *****/

plugins/c9.ide.terminal/terminal.js

@@ -356,6 +356,13 @@ define(function(require, exports, module) {
                 }
             });
         });
+        handle.on("unload", function(){
+            mnuTerminal = null;
+            lastEditor = null;
+            lastTerminal = null;
+            shownDotsHelp = null;
+            installPrompted = null;
+        });
         
         handle.draw = function(){
             ui.insertMarkup(null, markupMenu, handle);