[Redesign] Make ObjectBox Header conditional

Summary: Ref T8099. In cases like dashboards, we don't always want a header with ObjectBox. This makes it optional.

Test Plan: Review a tab panel, see no weird lines.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8099

Differential Revision: https://secure.phabricator.com/D12920

src/view/phui/PHUIObjectBoxView.php

@@ -159,10 +159,11 @@ final class PHUIObjectBoxView extends AphrontView {
       $header_color = $this->headerColor;
     }
 
+    $header = null;
     if ($this->header) {
       $header = $this->header;
       $header->setHeaderColor($header_color);
-    } else {
+    } else if ($this->headerText) {
       $header = id(new PHUIHeaderView())
         ->setHeader($this->headerText)
         ->setHeaderColor($header_color);