Update JD collection class

Author: emmanue1

src/main/java/org/jd/core/v1/util/Base.java

@@ -25,7 +25,7 @@ default T getLast() {
     }
 
     default DefaultList<T> getList() {
-        return (DefaultList<T>)this;
+        throw new UnsupportedOperationException();
     }
 
     default int size() {

src/main/java/org/jd/core/v1/util/DefaultList.java

@@ -66,6 +66,10 @@ public boolean isList() {
         return true;
     }
 
+    public DefaultList<E> getList() {
+        return this;
+    }
+
     public static <T> DefaultList<T> emptyList() {
         return EMPTY_LIST;
     }