Fix two warnings

src/konqsessionmanager.cpp

@@ -92,7 +92,7 @@ static const QList<KConfigGroup> windowConfigGroups(/*NOT const, we'll use write
 }
 
 SessionRestoreDialog::SessionRestoreDialog(const QStringList &sessionFilePaths, QWidget *parent)
-    : QDialog(parent, nullptr)
+    : QDialog(parent)
     , m_sessionItemsCount(0)
     , m_dontShowChecked(false)
 {

src/ktabwidget.h

@@ -47,7 +47,7 @@ public:
      * @param parent The parent widgets.
      * @param flags The Qt window flags @see QWidget.
      */
-    explicit KTabWidget(QWidget *parent = nullptr, Qt::WindowFlags flags = nullptr);
+    explicit KTabWidget(QWidget *parent = nullptr, Qt::WindowFlags flags = {});
 
     /**
      * Destroys the tab widget.