retain the pipe root for the action.

Author: Sigmonia

flow/src/org/labkey/flow/controllers/FlowController.java

@@ -299,10 +299,11 @@ public void addNavTrail(NavTree root)
     @RequiresPermission(AdminOperationsPermission.class)
     public class FlowAdminAction extends FormViewAction<FlowAdminForm>
     {
+        private final PipeRoot root = PipelineService.get().findPipelineRoot(getContainer());
+
         @Override
         public void validateCommand(FlowAdminForm form, Errors errors)
         {
-            PipeRoot root = PipelineService.get().findPipelineRoot(getContainer());
             if (root == null)
                 errors.rejectValue("root", ERROR_MSG, "Pipeline root not found for the current container.");
         }
@@ -317,8 +318,6 @@ public ModelAndView getView(FlowAdminForm form, boolean reshow, BindException er
         @Override
         public boolean handlePost(FlowAdminForm form, BindException errors)
         {
-            PipeRoot root = PipelineService.get().findPipelineRoot(getContainer());
-
             if (form.getWorkingDirectory() != null && root.getRootFileLike().isDescendant(FileUtil.createUri(form.getWorkingDirectory())))
             {
                 FileLike dir = root.resolvePathToFileLike(form.getWorkingDirectory());