Fix two issues with unusual milestone workboard initialization orders

Summary: Fixes T10316. Fixes T10311.

Test Plan:
  - Create a project, create a milestone, go back to the parent, go to the workboard. Previously, fatal. Now, prompts you to create workboard.
  - Create a project, create a milestone, create the parent workboard, put a task in the milestone's column, go to the milestone workboard. Previously, fatal. Now, prompts you to create workboard.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10311, T10316

Differential Revision: https://secure.phabricator.com/D15232

src/applications/project/controller/PhabricatorProjectBoardViewController.php

@@ -126,11 +126,21 @@ final class PhabricatorProjectBoardViewController
 
     $columns = $layout_engine->getColumns($board_phid);
     if (!$columns || !$project->getHasWorkboard()) {
+      $has_normal_columns = false;
+
+      foreach ($columns as $column) {
+        if (!$column->getProxyPHID()) {
+          $has_normal_columns = true;
+          break;
+        }
+      }
+
       $can_edit = PhabricatorPolicyFilter::hasCapability(
         $viewer,
         $project,
         PhabricatorPolicyCapability::CAN_EDIT);
-      if (!$columns) {
+
+      if (!$has_normal_columns) {
         if (!$can_edit) {
           $content = $this->buildNoAccessContent($project);
         } else {