Fix compatible issue.

Author: sutra

webmagic-core/src/main/java/us/codecraft/webmagic/SpiderListener.java

@@ -8,13 +8,14 @@
  */
 public interface SpiderListener {
 
-    public void onSuccess(Request request);
+    void onSuccess(Request request);
 
     /**
      * @deprecated Use {@link #onError(Request, Exception)} instead.
      */
     @Deprecated
-    public void onError(Request request);
+    default void onError(Request request) {
+    }
 
     default void onError(Request request, Exception e) {
         this.onError(request);

webmagic-core/src/main/java/us/codecraft/webmagic/downloader/AbstractDownloader.java

@@ -38,6 +38,11 @@ public Html download(String url, String charset) {
     protected void onSuccess(Request request) {
     }
 
+    @Deprecated
+    protected void onError(Request request) {
+        this.onError(request, null);
+    }
+
     protected void onError(Request request, Throwable e) {
     }