(fix) delete messages from Drafts folder that aren't meant to be sent

UI/WebServerResources/js/Mailer/MessageEditorController.js

@@ -133,10 +133,12 @@
     }
 
     function cancel() {
-      // TODO: delete draft?
       if (vm.autosave)
         $timeout.cancel(vm.autosave);
 
+      if (vm.message.isNew && vm.message.attachmentAttrs)
+        vm.message.$mailbox.$deleteMessages([vm.message]);
+
       $mdDialog.cancel();
     }