lightbox: make sure this.shown set to false when start showing

js/ui/lightbox.js

@@ -102,6 +102,7 @@ const Lightbox = new Lang.Class({
 
     show: function() {
         if (this._fadeInTime) {
+            this.shown = false;
             this.actor.opacity = 0;
             Tweener.addTween(this.actor,
                              { opacity: 255 * this._fadeFactor,

js/ui/screenShield.js

@@ -61,6 +61,7 @@ const ScreenShield = new Lang.Class({
             this._lightbox.show();
         } else {
             let lightboxWasShown = this._lightbox.shown;
+            log("this._lightbox.shown " + this._lightbox.shown);
             this._lightbox.hide();
             if (lightboxWasShown && this._settings.get_boolean(LOCK_ENABLED_KEY)) {
                 this._background.show();