Fix wrong 'tracker error' count

This happens when a torrent contains some tracker URLs that share the same domain.
Closes #17808.

src/gui/transferlistfilterswidget.cpp

@@ -70,11 +70,14 @@ namespace
         return !scheme.isEmpty() ? scheme : u"http"_qs;
     }
 
-    QString getHost(const QString &tracker)
+    QString getHost(const QString &url)
     {
         // We want the domain + tld. Subdomains should be disregarded
-        const QUrl url {tracker};
-        const QString host {url.host()};
+        // If failed to parse the domain or IP address, original input should be returned
+
+        const QString host = QUrl(url).host();
+        if (host.isEmpty())
+            return url;
 
         // host is in IP format
         if (!QHostAddress(host).isNull())
@@ -505,10 +508,8 @@ void TrackerFiltersList::addItems(const QString &trackerURL, const QVector<BitTo
 void TrackerFiltersList::removeItem(const QString &trackerURL, const BitTorrent::TorrentID &id)
 {
     const QString host = getHost(trackerURL);
-    QSet<BitTorrent::TorrentID> torrentIDs = m_trackers.value(host).torrents;
-    if (torrentIDs.empty())
-        return;
 
+    QSet<BitTorrent::TorrentID> torrentIDs = m_trackers.value(host).torrents;
     torrentIDs.remove(id);
 
     QListWidgetItem *trackerItem = nullptr;