Qt: advanced capture: fix mrl generation for advanced options

(cherry picked from commit f1790cf4624b2ecba773d540661c62dd51483e87)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/qt4/components/open_panels.cpp

@@ -1160,7 +1160,7 @@ void CaptureOpenPanel::updateMRL()
     }
     emit methodChanged( "live-caching" );
 
-    if( !advMRL.isEmpty() ) mrl += advMRL;
+    if( !advMRL.isEmpty() ) mrl += " " + advMRL;
 
     emit mrlUpdated( fileList, mrl );
 }