Use EXPAND_FRAMES class reader flags in class transformer (#124)

Relates to neoforged/NeoForge#768

(cherry picked from commit f1f25dc)

src/main/java/cpw/mods/modlauncher/ClassTransformer.java

@@ -73,7 +73,7 @@ byte[] transform(byte[] inputClass, String className, final String reason) {
         boolean empty;
         if (inputClass.length > 0) {
             final ClassReader classReader = new ClassReader(inputClass);
-            classReader.accept(clazz, 0);
+            classReader.accept(clazz, ClassReader.EXPAND_FRAMES);
             digest = ()->getSha256().digest(inputClass);
             empty = false;
         } else {