Allow whitespace on background-images, w3 compliance

js/reveal.js

@@ -3085,7 +3085,7 @@
 
 				// Images
 				if( backgroundImage ) {
-					background.style.backgroundImage = 'url('+ backgroundImage +')';
+					background.style.backgroundImage = 'url('+ encodeURI(backgroundImage) +')';
 				}
 				// Videos
 				else if ( backgroundVideo && !isSpeakerNotes() ) {