Unregister window observer before theme manager is deallocated

Technically this probably isn't actually necessary since ThemeManager looks like it should remain allocated until the program quits, but...

Signed-off-by: Kenneth Chew <79120643+kthchew@users.noreply.github.com>

launcher/ui/themes/ThemeManager.cpp

@@ -50,6 +50,11 @@ ThemeManager::ThemeManager()
     initializeCatPacks();
 }
 
+ThemeManager::~ThemeManager()
+{
+    stopSettingNewWindowColorsOnMac();
+}
+
 /// @brief Adds the Theme to the list of themes
 /// @param theme The Theme to add
 /// @return Theme ID
@@ -179,6 +184,8 @@ void ThemeManager::setTitlebarColorOnMac(WId windowId, QColor color)
 {}
 void ThemeManager::setTitlebarColorOfAllWindowsOnMac(QColor color)
 {}
+void ThemeManager::stopSettingNewWindowColorsOnMac()
+{}
 #endif
 
 QList<IconTheme*> ThemeManager::getValidIconThemes()

launcher/ui/themes/ThemeManager.h

@@ -39,6 +39,7 @@ inline auto themeWarningLog()
 class ThemeManager {
    public:
     ThemeManager();
+    ~ThemeManager();
 
     QList<IconTheme*> getValidIconThemes();
     QList<ITheme*> getValidApplicationThemes();
@@ -86,6 +87,8 @@ class ThemeManager {
     // This also will set the titlebar color of newly opened windows after this method is called.
     // On non-Mac systems, this is a no-op.
     void setTitlebarColorOfAllWindowsOnMac(QColor color);
+    // On non-Mac systems, this is a no-op.
+    void stopSettingNewWindowColorsOnMac();
 #ifdef Q_OS_MACOS
     NSObject* m_windowTitlebarObserver = nullptr;
 #endif

launcher/ui/themes/ThemeManager.mm

@@ -53,10 +53,7 @@ void ThemeManager::setTitlebarColorOfAllWindowsOnMac(QColor color)
     // There's no notification for when a new window is opened, but we can set the color when a window switches
     // from occluded to visible, which also fires on open.
     NSNotificationCenter* center = [NSNotificationCenter defaultCenter];
-    if (m_windowTitlebarObserver) {
-        [center removeObserver:m_windowTitlebarObserver];
-        m_windowTitlebarObserver = nil;
-    }
+    stopSettingNewWindowColorsOnMac();
     m_windowTitlebarObserver = [center addObserverForName:NSWindowDidChangeOcclusionStateNotification
                                                    object:nil
                                                     queue:[NSOperationQueue mainQueue]
@@ -65,3 +62,12 @@ void ThemeManager::setTitlebarColorOfAllWindowsOnMac(QColor color)
                                                    setTitlebarColorOnMac((WId)window.contentView, color);
                                                }];
 }
+
+void ThemeManager::stopSettingNewWindowColorsOnMac()
+{
+    if (m_windowTitlebarObserver) {
+        NSNotificationCenter* center = [NSNotificationCenter defaultCenter];
+        [center removeObserver:m_windowTitlebarObserver];
+        m_windowTitlebarObserver = nil;
+    }
+}