Early exit on empty sets.

src/engine/gameManager/DbManager.java

@@ -273,6 +273,11 @@ public enum DbManager {
 
         EnumSet<E> enumSet = EnumSet.noneOf(enumClass);
 
+        // Early exit for empty sets
+
+        if (mysqlSet.isEmpty())
+            return enumSet;
+
         // Remove the leading and trailing brackets from the MySQL set
 
         mysqlSet = mysqlSet.substring(1, mysqlSet.length() - 1);