Make removing a transform not crash.

sky/tests/styles/transforms.sky

Index: sky/tests/styles/transforms.sky
diff --git a/sky/tests/styles/transforms.sky b/sky/tests/styles/transforms.sky
index 9473c915ea7cb736a745ce702bf0b2d7bde03e90..49c44de47618fbf3913127e9aabb524431d52cfc 100644
--- a/sky/tests/styles/transforms.sky
+++ b/sky/tests/styles/transforms.sky
@@ -48,5 +48,12 @@
     test('scale should roundtrip', () {
       testTransformRoundTrip('scale(1.2, 0.8)', 'matrix(1.2, 0, 0, 0.8, 0, 0)');
     });
+
+    test('removing a transform should not crash', () {
+      testBox.style['transform'] = 'translate(0, 0, 0)';
+      testBox.getBoundingClientRect();
+      testBox.style.removeProperty('transform');
+      testBox.getBoundingClientRect();
+    });
   }
 </script>