Fix plugin registration trying to access the CreditsController in headless mode.

Author: leMaik

chunky/src/java/se/llbit/chunky/main/Chunky.java

@@ -58,7 +58,6 @@
 import java.util.*;
 import java.util.concurrent.ForkJoinPool;
 import java.util.stream.Collectors;
-import java.util.stream.Stream;
 
 /**
  * Chunky is a Minecraft mapping and rendering tool created byJesper Öqvist (jesper@llbit.se).
@@ -280,7 +279,9 @@ private void loadPlugins() {
     pluginManager.load(pluginManifests, (plugin, manifest) -> {
       String jarName = manifest.pluginJar.getName();
       Log.infof("Loading plugin: %s", jarName);
-      CreditsController.addPlugin(manifest.name, manifest.version.toString(), manifest.author, manifest.description);
+      if (!isHeadless()) {
+        CreditsController.addPlugin(manifest.name, manifest.version.toString(), manifest.author, manifest.description);
+      }
 
       try {
         plugin.attach(this);