fix：订阅重复下载问题

app/chain/download.py

@@ -357,6 +357,7 @@ class DownloadChain(ChainBase):
             need = list(set(_need).difference(set(_current)))
             # 清除已下载的季信息
             seas = copy.deepcopy(no_exists.get(_mid))
+            if seas:
                 for _sea in list(seas):
                     if _sea not in need:
                         no_exists[_mid].pop(_sea)
@@ -490,6 +491,9 @@ class DownloadChain(ChainBase):
                                 need_season = __update_seasons(_mid=need_mid,
                                                                _need=need_season,
                                                                _current=torrent_season)
+                                if not need_season:
+                                    # 全部下载完成
+                                    break
         # 电视剧季内的集匹配
         if no_exists:
             # TMDBID列表