Fix flameshot not exiting when it should (#2223)

* Remove unused methods from Controller

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

* Fix flameshot exit bug

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

* Remove unnecessary code

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

* Some more refactoring

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

src/widgets/capturelauncher.cpp

@@ -22,6 +22,7 @@
 CaptureLauncher::CaptureLauncher(QDialog* parent)
   : QDialog(parent)
 {
+    qApp->installEventFilter(this); // see eventFilter()
     setAttribute(Qt::WA_DeleteOnClose);
     setWindowIcon(QIcon(GlobalValues::iconPath()));
     m_imageLabel = new ImageLabel(this);