CCU: create progress bar only if task has children

If the task has no children it doesn't make much sense
to display the progress bar as the progress can only be 0 or 100%

src/applications/project/view/ProjectBoardTaskCard.php

@@ -199,8 +199,12 @@ final class ProjectBoardTaskCard extends Phobject {
         ->setIcon('fa-circle ' . $rag_status);
       $card->addAttribute($rag_icon);
 
-      $task_progress = $task->getTaskProgress($viewer);
-      if ($task_progress['total_points'] > 0) {
+      $task_children = $task->loadDependsOnTaskPHIDs();
+      $task_progress = [];
+      if ($task_children) {
+        $task_progress = $task->getTaskProgress($viewer);
+      }
+      if ($task_children && $task_progress['total_points'] > 0) {
         $bar = id(new PHUISegmentBarView())
           ->setLabel(pht(
             'Progress: %s/%s points',