AppBar with AppBarUtils navigation not working

AppBar with AppBarUtils navigation not working

I have this bug in my solution:
Exception
An unhandled exception of type 'System.NullReferenceException' occurred
in AppBarUtils.dll
XAML
<controls:Pivot Background="#FF10662B" Foreground="White"
BorderBrush="Black" >
<i:Interaction.Triggers>
<abu:SelectedPivotItemChangedTrigger>
<abu:SwitchAppBarAction>
<abu:AppBar Id="0">
<abu:AppBar.MenuItems>
<abu:AppBarMenuItem Text="Za³ó¿ konto"
Command="{Binding
NavigateCommand,Mode=TwoWay}"/>
</abu:AppBar.MenuItems>
<abu:AppBarButton IconUri="{Binding
AddButtonIcon}"
Text="Navigation" >
<ec:NavigateToPageAction
TargetPage="/LoginPage.xaml"/>
</abu:AppBarButton>
</abu:AppBar>
</abu:SwitchAppBarAction>
</abu:SelectedPivotItemChangedTrigger>
</i:Interaction.Triggers>
<--rest code with other pivots -->
</phone:PhoneApplicationPage>
Maybe I can use another way use navigation to page? How I can navigate to
different page with mvvm?