Fixed issue with binding when binding to a falsy object (also added types.isNullOrundefined function).

ui/core/bindable.ts

@@ -44,7 +44,7 @@ export class Bindable extends dependencyObservable.DependencyObservable implemen
         if (!bindingSource) {
             bindingSource = this.bindingContext;
         }
-        if (bindingSource) {
+        if (!types.isNullOrUndefined(bindingSource)) {
             binding.bind(bindingSource);
         }
     }
@@ -109,7 +109,7 @@ export class Bindable extends dependencyObservable.DependencyObservable implemen
                 " targetProperty: " + binding.options.targetProperty +
                 " to the changed context: " + newValue, trace.categories.Binding);
             binding.unbind();
-            if (newValue) {
+            if (!types.isNullOrUndefined(newValue)) {
                 binding.bind(newValue);
             }
         }
@@ -134,7 +134,7 @@ export class Binding {
     }
 
     public bind(obj: Object) {
-        if (!obj) {
+        if (types.isNullOrUndefined(obj)) {
             throw new Error("Expected valid object reference as a source in the Binding.bind method.");
         }
 
@@ -344,7 +344,7 @@ export class Binding {
                 currentObject = currentObject[properties[i]];
             }
 
-            if (currentObject !== undefined && currentObject !== null) {
+            if (!types.isNullOrUndefined(currentObject)) {
                 options = {
                     instance: new WeakRef(currentObject),
                     property: properties[properties.length - 1]

ui/tab-view/tab-view.android.ts

@@ -4,6 +4,7 @@ import dependencyObservable = require("ui/core/dependency-observable");
 import view = require("ui/core/view");
 import trace = require("trace");
 import imageSource = require("image-source");
+import types = require("utils/types");
 
 var VIEWS_STATES = "_viewStates";
 
@@ -436,7 +437,7 @@ export class TabView extends common.TabView {
     }
 
     private _setNativeSelectedIndex(index: number) {
-        if (index === undefined || index === null) {
+        if (types.isNullOrUndefined(index)) {
             return;
         }
 

ui/tab-view/tab-view.ios.ts

@@ -6,6 +6,7 @@ import trace = require("trace");
 import utils = require("utils/utils");
 import view = require("ui/core/view");
 import imageSource = require("image-source");
+import types = require("utils/types");
 
 // merge the exports of the common file with the exports of this file
 declare var exports;
@@ -206,7 +207,7 @@ export class TabView extends common.TabView {
 
         var newIndex = data.newValue;
         trace.write("TabView._onSelectedIndexPropertyChangedSetNativeValue(" + newIndex + ")", trace.categories.Debug);
-        if (newIndex === undefined || newIndex === null) {
+        if (types.isNullOrUndefined(newIndex)) {
             return;
         }