Prevent test fails for the npm build.

test/test.js

@@ -10399,6 +10399,7 @@
         function callback() {
           actual = this;
         }
+        if (func) {
           if (/^reduce/.test(methodName) || methodName == 'transform') {
             func(array, callback, 0, null);
           } else if (_.contains(['assign', 'merge'], methodName)) {
@@ -10411,6 +10412,10 @@
             func(array, callback, null);
           }
           strictEqual(actual, expected, message);
+        }
+        else {
+          skipTest();
+        }
       });
     });