Prevent navigator nodes from showing in create room category listing

Fixes #78

Author: Quackster

Kepler-Server/src/main/java/org/alexdev/kepler/messages/incoming/navigator/GETUSERFLATCATS.java

@@ -24,6 +24,10 @@ public void handle(Player player, NettyRequest reader) {
                 continue;
             }
 
+            if (category.isNode()) {
+                continue;
+            }
+            
             categoryList.add(category);
         }