1 files changed, 5 insertions, 3 deletions
diff --git a/js/shader.js b/js/shader.js
index 4a6e950..a8559ba 100644
--- a/js/shader.js
+++ b/js/shader.js
@@ -1,3 +1,5 @@
+function shader (x,y,t,d) {}
+
 var shader_build = function(){
   var fn_str = document.getElementById('shader').value
   if (!fn_str.length) fn_str = ""
@@ -16,7 +18,7 @@ var shader_build = function(){
 }
 
 var r,g,b,a;
-
+var w, h, actual_w, actual_h;
 function shade_no_error_handling(frame, t){
   if (! t || isNaN(t)) throw Error ("No time specified")
   if (! frame) throw Error ("No frame specified")
@@ -46,7 +48,7 @@ var firefox_stack_regexp = /:([0-9]+)$/;
 
 function shade_error_handling(frame, t){
   if (! t || isNaN(t)) throw Error ("No time specified")
-  if (! frame) throw Error ("No frame specified")
+  if (! frame || ! frame.ctx || ! frame.cloneData) throw Error ("No frame specified")
 
   var imgData = frame.ctx.getImageData(0,0,w,h)
   var data = imgData.data
@@ -77,7 +79,7 @@ function shade_error_handling(frame, t){
 
     } else if (lines.length > 1) { // attempt chrome match
       var matches = lines[1].match(chrome_stack_regexp)
-      if (matches.length > 1)
+      if (matches && matches.length > 1)
         error_highlight.on(parseInt(matches[1]) - 3)
     }