Don't call QElapsedTimer::restart on uninitialized timer

That's an undefined behavior.
Since we don't use the return value anyway, we should just use start()

src/gui/accountstate.cpp

@@ -160,7 +160,7 @@ bool AccountState::isConnected() const
 
 void AccountState::tagLastSuccessfullETagRequest()
 {
-    _timeSinceLastETagCheck.restart();
+    _timeSinceLastETagCheck.start();
 }
 
 void AccountState::checkConnectivity()

src/gui/activitywidget.cpp

@@ -348,7 +348,7 @@ void ActivityWidget::slotBuildNotificationDisplay(const ActivityList &list)
 
     if (newGuiLogCount > 0) {
         // restart the gui log timer now that we show a notification
-        _guiLogTimer.restart();
+        _guiLogTimer.start();
 
         // Assemble a tray notification
         QString msg = tr("You received %n new notification(s) from %2.", "", accNotified[accNotified.keys().at(0)]).arg(accNotified.keys().at(0));

src/gui/folder.cpp

@@ -629,7 +629,7 @@ void Folder::startSync(const QStringList &pathList)
     }
     _csyncUnavail = false;
 
-    _timeSinceLastSyncStart.restart();
+    _timeSinceLastSyncStart.start();
     _syncResult.setStatus(SyncResult::SyncPrepare);
     emit syncStateChange();
 
@@ -798,7 +798,7 @@ void Folder::slotSyncFinished(bool success)
     QTimer::singleShot(200, this, SLOT(slotEmitFinishedDelayed()));
 
     _lastSyncDuration = _timeSinceLastSyncStart.elapsed();
-    _timeSinceLastSyncDone.restart();
+    _timeSinceLastSyncDone.start();
 
     // Increment the follow-up sync counter if necessary.
     if (anotherSyncNeeded == ImmediateFollowUp) {

src/libsync/discoveryphase.cpp

@@ -159,11 +159,11 @@ void DiscoveryJob::update_job_update_callback(bool local,
     if (updateJob) {
         // Don't wanna overload the UI
         if (!updateJob->_lastUpdateProgressCallbackCall.isValid()) {
-            updateJob->_lastUpdateProgressCallbackCall.restart(); // first call
+            updateJob->_lastUpdateProgressCallbackCall.start(); // first call
         } else if (updateJob->_lastUpdateProgressCallbackCall.elapsed() < 200) {
             return;
         } else {
-            updateJob->_lastUpdateProgressCallbackCall.restart();
+            updateJob->_lastUpdateProgressCallbackCall.start();
         }
 
         QByteArray pPath(dirUrl);