avoid errors in dead code

camp/static/js/slideshow.js

@@ -34,30 +34,15 @@ document.querySelectorAll('.select-image').forEach(function(a) {
     };
 });
 
-/*
-if (document.querySelectorAll('.select-image').length && document.location.hash.length) {
-    var slide = parseInt(document.location.hash.slice(1))
-    if (slide) {
-        slider.goToSlide(slide - 1)
-        slider.resize()
-        slider.redrawSlider()
-        setTimeout(function() {
-            slider.resize()
-            slider.redrawSlider()
-        }, 2000)
-    }
-}
-*/
-
 $(document).keydown(function(e){
     if (e.keyCode == 39) // Right arrow 
         {
-            slider && slider.goToNextSlide();
+            slider && slider.goToNextSlide && slider.goToNextSlide();
             return false;
         }
     else if (e.keyCode == 37) // left arrow
         {
-            slider && slider.goToPrevSlide();
+            slider && slider.goToPrevSlide && slider.goToPrevSlide();
             return false;
        }
  });