Fix memory leaks

* Fixes a couple of memory leaks (although not dangerous in practice, since we are talking about objects with a lifetime up to the end of the application)
* Fixes heap use after free

PR qbittorrent#19650.
Closes qbittorrent#19632.

src/base/http/requestparser.cpp

@@ -212,7 +212,7 @@ bool RequestParser::parseRequestLine(const QString &line)
 
     if (sepPos >= 0)
     {
-        const QByteArrayView query = url.mid(sepPos + 1);
+        const QByteArrayView query = QByteArrayView(url).mid(sepPos + 1);
 
         // [rfc3986] 2.4 When to Encode or Decode
         // URL components should be separated before percent-decoding

src/base/torrentfileswatcher.cpp

@@ -159,7 +159,7 @@ void TorrentFilesWatcher::initWorker()
     connect(m_asyncWorker, &TorrentFilesWatcher::Worker::torrentFound, this, &TorrentFilesWatcher::onTorrentFound);
 
     m_asyncWorker->moveToThread(m_ioThread.get());
-    connect(m_ioThread.get(), &QThread::finished, this, [this] { delete m_asyncWorker; });
+    connect(m_ioThread.get(), &QObject::destroyed, this, [this] { delete m_asyncWorker; });
     m_ioThread->start();
 
     for (auto it = m_watchedFolders.cbegin(); it != m_watchedFolders.cend(); ++it)

src/gui/lineedit.cpp

@@ -38,7 +38,7 @@
 LineEdit::LineEdit(QWidget *parent)
     : QLineEdit(parent)
 {
-    auto *action = new QAction(UIThemeManager::instance()->getIcon(u"edit-find"_s), QString());
+    auto *action = new QAction(UIThemeManager::instance()->getIcon(u"edit-find"_s), QString(), this);
     addAction(action, QLineEdit::LeadingPosition);
 
     setClearButtonEnabled(true);