Core: Consistently use nullptr

Fixed by clang-tidy modernize-use-nullptr.

Change-Id: I62a9388ab873410555f45a8a6f9b0149467ddbaa
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/coreplugin/basefilewizard.h

@@ -43,7 +43,7 @@ class CORE_EXPORT BaseFileWizard : public Utils::Wizard
 
 public:
     explicit BaseFileWizard(const BaseFileWizardFactory *factory, const QVariantMap &extraValues,
-                            QWidget *parent = 0);
+                            QWidget *parent = nullptr);
 
     void initializePage(int id) override;
 
@@ -58,7 +58,7 @@ private:
     QVariantMap m_extraValues;
     const BaseFileWizardFactory *m_factory;
     QList<QWizardPage *> m_extensionPages;
-    QWizardPage *m_firstExtensionPage = 0;
+    QWizardPage *m_firstExtensionPage = nullptr;
     GeneratedFiles m_files;
 };