Qt4: add title to file associations dialog

Currently, when you click the button to set up file associations on
Windows, the dialog presented is untitled and just displays the file
name, "vlc".

Close #5711
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/qt4/components/simple_preferences.cpp

@@ -945,6 +945,7 @@ void SPrefsPanel::assoDialog()
     CoUninitialize();
 
     QDialog *d = new QDialog( this );
+    d->setWindowTitle( qtr( "File associations" ) );
     QGridLayout *assoLayout = new QGridLayout( d );
 
     QTreeWidget *filetypeList = new QTreeWidget;