Disallow contentless ponder questions

Test Plan:
* submitted various comments (empty, whitespace, real) and
verified response

Reviewers: pieter, epriestley

CC: vrana, aran, Korvin

Maniphest Tasks: T1644

Differential Revision: https://secure.phabricator.com/D3505

src/applications/ponder/controller/PonderCommentSaveController.php

@@ -40,6 +40,16 @@ final class PonderCommentSaveController extends PonderController {
     }
     $content = $request->getStr('content');
 
+    if (!strlen(trim($content))) {
+      $dialog = new AphrontDialogView();
+      $dialog->setUser($request->getUser());
+      $dialog->setTitle('Empty comment');
+      $dialog->appendChild('<p>Your comment must not be empty.</p>');
+      $dialog->addCancelButton('/Q'.$question_id);
+
+      return id(new AphrontDialogResponse())->setDialog($dialog);
+    }
+
     $res = new PonderComment();
     $res
       ->setContent($content)
@@ -51,8 +61,7 @@ final class PonderCommentSaveController extends PonderController {
 
     return id(new AphrontRedirectResponse())
       ->setURI(
-        id(new PhutilURI('/Q'. $question->getID()))
-        ->setFragment('comment-' . $res->getID()));
+        id(new PhutilURI('/Q'. $question->getID())));
   }
 
 }

src/applications/ponder/view/PonderAddCommentView.php

@@ -55,6 +55,7 @@ final class PonderAddCommentView extends AphrontView {
     $form
       ->setUser($this->user)
       ->setAction($this->actionURI)
+      ->setWorkflow(true)
       ->addHiddenInput('target', $target)
       ->addHiddenInput('question_id', $questionID)
       ->appendChild(