escapeHtml was being called with integer values (specifically task_list.id which is sometimes an integer)

Author: akhatua2

viewer.html

@@ -1271,7 +1271,8 @@ <h1 class="text-2xl font-semibold text-gray-900 mb-2">Trajectory Viewer</h1>
             }
 
             function escapeHtml(str) {
-                return str
+                if (str == null) return '';
+                return String(str)
                     .replace(/&/g, "&amp;")
                     .replace(/</g, "&lt;")
                     .replace(/>/g, "&gt;");