implement review comment by @ahocevar

test/expect-0.2.0-ol3/expect.js

@@ -318,18 +318,10 @@
         }
         // test attribute namespace
         try {
-          var uri1 = node1Attr[name].namespaceURI;
-          var uri2 = node2Attr[name].namespaceURI;
           // we do not care about the difference between an empty string and null for namespaceURI
           // some tests will fail in IE9 otherwise
           // see also http://msdn.microsoft.com/en-us/library/ff460650(v=vs.85).aspx
-          if (uri1 == '') {
-            uri1 = null;
-          }
-          if (uri2 == '') {
-            uri2 = null;
-          }
-          expect(uri1).to.equal(uri2);
+          expect(node1Attr[name].namespaceURI || null).to.be(node2Attr[name].namespaceURI || null);
         } catch(e) {
           errors.push('namespaceURI attribute test failed for: ' + node1.nodeName + ' | ' + e.message);
         }