Handle non-invertible matrices in Item#contains() (#1651)

src/item/Item.js

@@ -1816,8 +1816,11 @@ new function() { // Injection scope for various item event handlers
      */
     contains: function(/* point */) {
         // See CompoundPath#_contains() for the reason for !!
-        return !!this._contains(
+        var matrix = this._matrix;
-                this._matrix._inverseTransform(Point.read(arguments)));
+        return (
+            matrix.isInvertible() && 
+            !!this._contains(matrix._inverseTransform(Point.read(arguments)))
+        );
     },
 
     _contains: function(point) {

test/tests/Item.js

@@ -877,6 +877,25 @@ test('Item#pivot', function() {
             'Changing position of an item with applyMatrix = true should change pivot');
 });
 
+test('Item#contains', function() {
+    var point = new Point(50,50);
+    var path1 = new Path({matrix: new Matrix(0,0,0,0,0,0)});
+    
+    equals(path1.contains(point), false,
+            'An irregularly shaped item cannot contain a point');
+
+    var path2 = new Path.Rectangle({
+        point: [50, 50],
+        size: [100, 100]
+    });
+    equals(path2.contains(point), true,
+            'A regularly shaped item with a point inside it, contains that point');
+
+    var point2 = new Point(0,0);
+    equals(path2.contains(point2), false,
+            'A regularly shaped item with a point outside it, does not contain that point');
+});
+
 test('Item#position with irregular shape, #pivot and rotation', function() {
     var path1 = new Path([ [0, 0], [200, 100], [0, 100] ]);
     var path2 = path1.clone();