Make the class items node consistent with the rest.

Supposedly, this doesn't actually do much, but the code now looks like the rest of the "string or string list" parsing.

src/main/java/com/garbagemule/MobArena/ArenaMasterImpl.java

@@ -376,7 +376,10 @@ public class ArenaMasterImpl implements ArenaMaster
     private void loadClassItems(ConfigurationSection section, ArenaClass arenaClass) {
         List<String> items = section.getStringList("items");
         if (items == null || items.isEmpty()) {
-            String value = section.getString("items", "");
+            String value = section.getString("items", null);
+            if (value == null || value.isEmpty()) {
+                return;
+            }
             items = Arrays.asList(value.split(","));
         }