diff --git a/src/infrastructure/editor/PhabricatorEditorURIEngine.php b/src/infrastructure/editor/PhabricatorEditorURIEngine.php
--- a/src/infrastructure/editor/PhabricatorEditorURIEngine.php
+++ b/src/infrastructure/editor/PhabricatorEditorURIEngine.php
@@ -279,10 +279,11 @@
     // editor links do surprising things with paths containing "/../".
 
     // Find anything that looks like "/../" and mangle it.
-
-    $token = preg_replace('((^|/)\.\.(/|\z))', '\1dot-dot\2', $token);
-
-    return phutil_escape_uri($token);
+    if (phutil_nonempty_string($token)) {
+      $token = preg_replace('((^|/)\.\.(/|\z))', '\1dot-dot\2', $token);
+      return phutil_escape_uri($token);
+    }
+    return '';
   }
 
   private function newStringFromTokens(array $tokens) {