Add no-args constructors for other quest classes

forge-gui/src/main/java/forge/quest/data/QuestAchievements.java

@@ -38,6 +38,9 @@ public class QuestAchievements {
     // Difficulty - will store only index from now.
     private int difficulty;
 
+    public QuestAchievements() { //needed for XML serialization
+    }
+
     /**
      * TODO: Write javadoc for Constructor.
      * @param diff   int

forge-gui/src/main/java/forge/quest/data/QuestAssets.java

@@ -165,6 +165,9 @@ public class QuestAssets {
         cond.setLevel(level);
     }
 
+    public QuestAssets() { //needed for XML serialization
+    }
+
     /**
      * Instantiates a new quest assets.
      */