refs #18875 [fid_bbi] add unknown media type icon

themes/fid_bbi/icons/big/unknown.svg

+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 84 84" height="84" width="84"><path d="M16 5h52v74H16z" fill="none" stroke="#000" stroke-width="2"/><path d="M34 28h16v12h-8v10" fill="none" stroke="#00a376" stroke-width="4"/><path fill="#00a376" d="M40 54h4v4h-4z" stroke="none"/></svg>

themes/fid_bbi/templates/RecordDriver/DefaultRecord/result-list.phtml

@@ -12,6 +12,8 @@ $formatIconMappings = json_decode(file_get_contents($formatIconMappingsFile), tr
 <div class="result_type">
   <?php if (!empty($formatIconMappings[$format])): ?>
     <?=$this->icon("big/{$formatIconMappings[$format]}")?>
+  <?php else: ?>
+    <?=$this->icon('big/unknown')?>
   <?php endif; ?>
 </div>