Sidemenu Icon disappear after upgrade to Beta 8

Ionic Framework ionic-v3
1

After I upgrade the code to ionic 2 beta 8 version, the sidemenu icon disappear in certain circumstance.
Anybody can advise?

Example:
GettingStartedPage (sidemenu icon appear) → test-1 page (disable sidemenu) → test-2 page (enable side menu, but the icon disappear from the view)

Code:
GettingStartedPage.html

<ion-navbar *navbar>
  <button menuToggle>
    <ion-icon name="menu"></ion-icon>
  </button>
  <ion-title>Getting Started</ion-title>
</ion-navbar>
<ion-content padding class="getting-started">
  <h3>Welcome to Ionic</h3>
  <p>Want to learn some facts?  Click below.</p>
  <button (click)="goPage1()">Test 1</button>
</ion-content>

test-1.html

<ion-navbar *navbar>
  <ion-title>test1</ion-title>
</ion-navbar>

<ion-content padding class="test-1">
  <button (click)="goPage2()">Test 2</button>
</ion-content>

test-2.html

<ion-navbar *navbar>
  <button menuToggle>
    <ion-icon name="menu"></ion-icon>
  </button>
  <ion-title>test2</ion-title>
</ion-navbar>

<ion-content padding class="test-2">

</ion-content>

image
GettingStartedPage.html - sidemenu icon appear

image
test-1.html - sidemenu icon was disable from the code

image
test-2.html - sidemenu icon enable from code but disappear in view