If windowHashChangeHandler and we perform Util.Events.remove() then w…

…e remove all event handlers from the 'hashchange' event. This means that jquerymobile will not be able to handle history.back() and you will remain in the same page.

src/photoswipe.class.js

@@ -476,7 +476,7 @@
 				Util.Events.remove(window.document, 'keydown', this.keyDownHandler);
 			}
 
-			if (this.isBackEventSupported && this.settings.backButtonHideEnabled){
+			if (this.isBackEventSupported && this.settings.backButtonHideEnabled && this.windowHashChangeHandler!=null){
 				Util.Events.remove(window, 'hashchange', this.windowHashChangeHandler);
 			}