Fix lint warning in CallTracker.

The previous code was using `== null` to handle both `null` and
`undefined`, resulting in a jshint warning. The conditional is meant to
check for non-primitive values, and it happens to be the case that a
falsey value in JS is always a primitive, or `null` or `undefined`.

src/core/CallTracker.js

@@ -14,7 +14,8 @@ getJasmineRequireObj().CallTracker = function(j$) {
         var str = Object.prototype.toString.apply(argsAsArray[i]),
           primitives = /^\[object (Boolean|String|RegExp|Number)/;
 
-        if (argsAsArray[i] == null || str.match(primitives)) {
+        // All falsey values are either primitives, `null`, or `undefined.
+        if (!argsAsArray[i] || str.match(primitives)) {
           clonedArgs.push(argsAsArray[i]);
         } else {
           clonedArgs.push(j$.util.clone(argsAsArray[i]));