Bump to v4.3.0.

subtract.js

@@ -14,6 +14,9 @@
  */
 function subtract(minuend, subtrahend) {
   var result;
+  if (minuend === undefined && subtrahend === undefined) {
+    return 0;
+  }
   if (minuend !== undefined) {
     result = minuend;
   }