It was found for /xwiki/bin/inline/Panels/Recently+Modified panel, but could affect also Recently Created and RecentlyVisited panels.
if user doesn't have access to the document, then $rdoc.displayTitle remains uninitialized and it is shown in panel list.
Simple fix is setting initial value for it:
<span class="pitemseparator"> | </span>
<span class="panelitem"><a href="$rdoc.getURL("view")">$title</a></span>