fixed missing check for Casper.options.httpStatusHandlers values

@@ -125,8 +125,10 @@ function createPage(casper) {
         }
         if (resource.url === casper.requestUrl && resource.stage === "start") {
             casper.currentHTTPStatus = resource.status;
-            if (isType(casper.options.httpStatusHandlers, "object") && resource.status in casper.options.httpStatusHandlers) {
-                casper.options.httpStatusHandlers[resource.status](casper, resource);
+            if (isType(casper.options.httpStatusHandlers, "object") &&
+                resource.status in casper.options.httpStatusHandlers &&
+                isType(casper.options.httpStatusHandlers[resource.status], "function")) {
+                casper.options.httpStatusHandlers[resource.status].call(casper, casper, resource);
             }
             casper.currentUrl = resource.url;
         }
@@ -228,7 +230,7 @@ function isWebPage(what) {
 function mergeObjects(obj1, obj2) {
     for (var p in obj2) {
         try {
-            if (obj2[p].constructor == Object) {
+            if (obj2[p].constructor === Object) {
                 obj1[p] = mergeObjects(obj1[p], obj2[p]);
             } else {
                 obj1[p] = obj2[p];