Use trackers from magnet link when calling get_metainfo

Author: egbertbouman

src/tribler/core/libtorrent/torrentdef.py

@@ -325,7 +325,8 @@ def load_only_sha1(infohash: bytes, name: str, url: str) -> TorrentDef:
         """
         This loads a TorrentDef with only the SHA-1, without resolving it from the given URI.
         """
-        atp = lt.add_torrent_params()
+        # Magnet links need to be parsed to avoid losing the trackers.
+        atp = lt.parse_magnet_uri(url) if url.startswith("magnet") else lt.add_torrent_params()
         atp.info_hash = lt.sha1_hash(infohash)
         atp.name = name
         atp.url = url