Track properties window lifetime via QPointer

Previously the properties window would sometimes not receive
a closeEvent, leaving a dangling pointer in OBSBasicMain (and resulting
in a crash when trying to open a new properties window or closing
the application)

obs/window-basic-main.cpp

@@ -979,8 +979,3 @@ config_t OBSBasic::Config() const
 {
 	return basicConfig;
 }
-
-void OBSBasic::UnloadProperties()
-{
-	properties = nullptr;
-}

obs/window-basic-main.hpp

@@ -25,6 +25,8 @@
 
 #include <util/util.hpp>
 
+#include <QPointer>
+
 class QListWidgetItem;
 
 #include "ui_OBSBasic.h"
@@ -45,7 +47,7 @@ private:
 
 	ConfigFile   basicConfig;
 
-	OBSBasicProperties *properties;
+	QPointer<OBSBasicProperties> properties;
 
 	void GetFPSCommon(uint32_t &num, uint32_t &den) const;
 	void GetFPSInteger(uint32_t &num, uint32_t &den) const;
@@ -103,8 +105,6 @@ public:
 	void SaveProject();
 	void LoadProject();
 
-	void UnloadProperties();
-
 protected:
 	virtual void closeEvent(QCloseEvent *event) override;
 	virtual void changeEvent(QEvent *event) override;

obs/window-basic-properties.cpp

@@ -78,12 +78,6 @@ void OBSBasicProperties::DrawPreview(void *data, uint32_t cx, uint32_t cy)
 	gs_matrix_pop();
 }
 
-void OBSBasicProperties::closeEvent(QCloseEvent *event)
-{
-	main->UnloadProperties();
-	UNUSED_PARAMETER(event);
-}
-
 void OBSBasicProperties::resizeEvent(QResizeEvent *event)
 {
 	if (isVisible()) {

obs/window-basic-properties.hpp

@@ -50,7 +50,6 @@ public:
 	void Init();
 
 protected:
-	virtual void closeEvent(QCloseEvent *event) override;
 	virtual void resizeEvent(QResizeEvent *event) override;
 	virtual void timerEvent(QTimerEvent *event) override;
 };