Fixed the fix of the fix of javaplugin.getResource

By: Nathan Adams <dinnerbone@dinnerbone.com>

paper-api/src/main/java/org/bukkit/plugin/java/JavaPlugin.java

@@ -153,6 +153,11 @@ public abstract class JavaPlugin implements Plugin {
 
         try {
             URL url = getClassLoader().getResource(filename);
+
+            if (url == null) {
+                return null;
+            }
+
             URLConnection connection = url.openConnection();
             connection.setUseCaches(false);
             return connection.getInputStream();