Fixed downloaded pages starting from -1

app/src/main/java/com/hippo/ehviewer/client/data/DownloadInfo.java

@@ -32,7 +32,7 @@ public class DownloadInfo {
     // byte/second, -1 for can't get speed now
     public long speed;
     // -1 for unknown
-    public int download = -1;
+    public int download = 0;
     // -1 for unknown
     public int total = -1;
     // Integer.MAX_VALUE for unknown

app/src/main/java/com/hippo/ehviewer/service/DownloadManager.java

@@ -473,7 +473,7 @@ public class DownloadManager {
     private void releaseCurrent() {
         if (mCurrentTask != null) {
             mCurrentTask.speed = -1;
-            mCurrentTask.download = -1;
+            mCurrentTask.download = 0;
             mCurrentTask.total = -1;
             mCurrentTask = null;
             mCurrentSpider.removeSpiderSpiderListener(mDownloadSpiderListener);