Fix resource loader threading issues

src/main/java/com/volmit/iris/core/loader/ResourceLoader.java

@@ -287,6 +287,8 @@ public class ResourceLoader<T extends IrisRegistrant> implements MeteredCache {
 
     public KList<File> getFolders() {
         if(folderCache.get() == null) {
+            synchronized(folderCache)
+            {
                 folderCache.set(new KList<>());
 
                 for(File i : root.listFiles()) {
@@ -298,6 +300,7 @@ public class ResourceLoader<T extends IrisRegistrant> implements MeteredCache {
                     }
                 }
             }
+        }
 
         return folderCache.get();
     }