改变分集的视频封面获取方法，避免出现bug

download/download.go

@@ -140,7 +140,7 @@ func MusicInfo(bv string) (info map[string]interface{}) {
 			info["videos"] = make(map[int]interface{})
 			pages := rjson["data"].(map[string]interface{})["pages"].([]interface{})
 			for page, videoInfo := range pages {
-				info["videos"].(map[int]interface{})[page+1] = map[string]interface{}{"title": videoInfo.(map[string]interface{})["part"].(string), "cover": videoInfo.(map[string]interface{})["first_frame"].(string), "duration": int(videoInfo.(map[string]interface{})["duration"].(float64))}
+				info["videos"].(map[int]interface{})[page+1] = map[string]interface{}{"title": videoInfo.(map[string]interface{})["part"].(string), "cover": rjson["data"].(map[string]interface{})["pic"].(string), "duration": int(videoInfo.(map[string]interface{})["duration"].(float64))}
 			}
 		}
 	})