layout: Fix the actor tracking parameter parsing

It's not appropriate to inherit from the parent property if we pass "false"
as a value, especially when all current parameters are booleans.

https://bugzilla.gnome.org/show_bug.cgi?id=660608

js/ui/layout.js

@@ -625,7 +625,7 @@ Chrome.prototype = {
         // We can't use Params.parse here because we want to drop
         // the extra values like ancestorData.actor
         for (let prop in defaultParams) {
-            if (!params[prop])
+            if (!params.hasOwnProperty(prop))
                 params[prop] = ancestorData[prop];
         }