Work around the crash occurred in QTimer

See Qt commit:
https://code.qt.io/cgit/qt/qtbase.git/commit/src/corelib/kernel/qtimer.cpp?id=a623fe8d2a60ff333d5779f877e3b20f0e141ff1

Fixes #9985.

src/webui/api/synccontroller.cpp

@@ -31,8 +31,8 @@
 #include <algorithm>
 
 #include <QJsonObject>
+#include <QMetaObject>
 #include <QThread>
-#include <QTimer>
 
 #include "base/bittorrent/peerinfo.h"
 #include "base/bittorrent/session.h"
@@ -335,7 +335,7 @@ SyncController::SyncController(ISessionManager *sessionManager, QObject *parent)
     connect(m_freeDiskSpaceChecker, &FreeDiskSpaceChecker::checked, this, &SyncController::freeDiskSpaceSizeUpdated);
 
     m_freeDiskSpaceThread->start();
-    QTimer::singleShot(0, m_freeDiskSpaceChecker, &FreeDiskSpaceChecker::check);
+    invokeChecker();
     m_freeDiskSpaceElapsedTimer.start();
 }
 
@@ -521,7 +521,7 @@ void SyncController::torrentPeersAction()
 qint64 SyncController::getFreeDiskSpace()
 {
     if (m_freeDiskSpaceElapsedTimer.hasExpired(FREEDISKSPACE_CHECK_TIMEOUT)) {
-        QTimer::singleShot(0, m_freeDiskSpaceChecker, &FreeDiskSpaceChecker::check);
+        invokeChecker();
         m_freeDiskSpaceElapsedTimer.restart();
     }
 
@@ -532,3 +532,12 @@ void SyncController::freeDiskSpaceSizeUpdated(qint64 freeSpaceSize)
 {
     m_freeDiskSpace = freeSpaceSize;
 }
+
+void SyncController::invokeChecker() const
+{
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 10, 0))
+    QMetaObject::invokeMethod(m_freeDiskSpaceChecker, &FreeDiskSpaceChecker::check, Qt::QueuedConnection);
+#else
+    QMetaObject::invokeMethod(m_freeDiskSpaceChecker, "check", Qt::QueuedConnection);
+#endif
+}

src/webui/api/synccontroller.h

@@ -56,6 +56,7 @@ private slots:
 
 private:
     qint64 getFreeDiskSpace();
+    void invokeChecker() const;
 
     qint64 m_freeDiskSpace = 0;
     FreeDiskSpaceChecker *m_freeDiskSpaceChecker = nullptr;