Debugger: Initialize members

m_toolbarDock was only initialized in finalizeSetup, which is triggered
by the plugin's initialize() method. This is not safe since Creator might
shut down before that method ever gets called.

Change-Id: Idadb6ac943ed6799d1bd9db1ecb884cb39038389
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/debuggermainwindow.h

@@ -146,7 +146,7 @@ private:
     QStackedWidget *m_centralWidgetStack;
     QWidget *m_editorPlaceHolder;
     Utils::StatusLabel *m_statusLabel;
-    QDockWidget *m_toolbarDock;
+    QDockWidget *m_toolbarDock = nullptr;
 
     QHash<QByteArray, QDockWidget *> m_dockForDockId;
     QHash<QByteArray, QWidget *> m_toolbarForPerspectiveId;