general: Replace 0 literals with nullptr where applicable

src/citra_qt/debugger/profiler.cpp

@@ -150,7 +150,7 @@ void ProfilerWidget::setProfilingInfoUpdateEnabled(bool enable)
 
 class MicroProfileWidget : public QWidget {
 public:
-    MicroProfileWidget(QWidget* parent = 0);
+    MicroProfileWidget(QWidget* parent = nullptr);
 
 protected:
     void paintEvent(QPaintEvent* ev) override;

src/citra_qt/debugger/profiler.h

@@ -53,7 +53,7 @@ class MicroProfileDialog : public QWidget {
     Q_OBJECT
 
 public:
-    MicroProfileDialog(QWidget* parent = 0);
+    MicroProfileDialog(QWidget* parent = nullptr);
 
     /// Returns a QAction that can be used to toggle visibility of this dialog.
     QAction* toggleViewAction();