avoid rendering graphic effects for null-extent canvasses

HISTORY.md

@@ -2,6 +2,7 @@
 
 ###2018-11-02
 * new library: Frequency Distribution Analysis, separated from "Bigger Data"
+* Objects: avoid rendering graphic effects for null-extent canvasses
 
 ## v4.2.2.4
 ###2018-10-29

src/objects.js

@@ -83,7 +83,7 @@ BlockEditorMorph, BlockDialogMorph, PrototypeHatBlockMorph, localize,
 TableMorph, TableFrameMorph, normalizeCanvas, BooleanSlotMorph, HandleMorph,
 AlignmentMorph, Process, XML_Element, VectorPaintEditorMorph*/
 
-modules.objects = '2018-October-23';
+modules.objects = '2018-November-02';
 
 var SpriteMorph;
 var StageMorph;
@@ -4034,6 +4034,10 @@ SpriteMorph.prototype.applyGraphicsEffects = function (canvas) {
     }
 
     if (this.graphicsChanged()) {
+        if (!canvas.width || !canvas.height) {
+            // too small to get image data, abort
+            return canvas;
+        }
         ctx = canvas.getContext("2d");
         imagedata = ctx.getImageData(0, 0, canvas.width, canvas.height);