Index: backend/models/Challenge.js
===================================================================
--- backend/models/Challenge.js	(revision e176d66bf79f1fac404e7a93d6dc99c64fca1ee0)
+++ backend/models/Challenge.js	(revision 892606063c1ff7dc46804e08ba0499bf9b478d5f)
@@ -2,6 +2,6 @@
   constructor(data = {}) {
     this.id = data.id;
-    this.title = data.title || '';
-    this.content = data.content || '';
+    this.title = data.title || "";
+    this.content = data.content || "";
     this.solving_date = data.solving_date;
     this.attempted_by = data.attempted_by;