fixed #1312

fixed collision detection for non-integer devicePixelRatios

gui.js

@@ -72,7 +72,7 @@ isRetinaSupported*/
 
 // Global stuff ////////////////////////////////////////////////////////
 
-modules.gui = '2016-July-15';
+modules.gui = '2016-July-17';
 
 // Declarations
 
@@ -2982,7 +2982,7 @@ IDE_Morph.prototype.aboutSnap = function () {
         module, btn1, btn2, btn3, btn4, licenseBtn, translatorsBtn,
         world = this.world();
 
-    aboutTxt = 'Snap! 4.0.8.1\nBuild Your Own Blocks\n\n'
+    aboutTxt = 'Snap! 4.0.8.2\nBuild Your Own Blocks\n\n'
         + 'Copyright \u24B8 2016 Jens M\u00F6nig and '
         + 'Brian Harvey\n'
         + 'jens@moenig.org, bh@cs.berkeley.edu\n\n'

history.txt

@@ -2965,3 +2965,9 @@ http://snap.berkeley.edu/run#cloud:Username=jens&ProjectName=rotation
 
 == v4.0.8.1 ====
 
+160717
+------
+* Morphic: fixed collision detection for non-integer devicePixelRatios
+
+== v4.0.8.2 ====
+

morphic.js

@@ -1103,7 +1103,7 @@
 
 /*global window, HTMLCanvasElement, FileReader, Audio, FileList*/
 
-var morphicVersion = '2016-July-14';
+var morphicVersion = '2016-July-17';
 var modules = {}; // keep track of additional loaded modules
 var useBlurredShadows = getBlurredShadowSupport(); // check for Chrome-bug
 
@@ -4114,9 +4114,13 @@ Morph.prototype.evaluateString = function (code) {
 
 Morph.prototype.isTouching = function (otherMorph) {
     var oImg = this.overlappingImage(otherMorph),
-        data = oImg.getContext('2d')
-            .getImageData(1, 1, oImg.width, oImg.height)
-            .data;
+        data;
+    if (!oImg.width || !oImg.height) {
+        return false;
+    }
+    data = oImg.getContext('2d')
+        .getImageData(1, 1, oImg.width, oImg.height)
+        .data;
     return detect(
         data,
         function (each) {