xaml - Empty collection bound to LongListSelector cause incorrect view of page -

i have windows phone 8 page has number of controls on it, of them longlistselector controls. if collections have content displayed correctly.

but if of collections bound lists empty controls below them on page disappear, i.e. page looks truncated lots of things missing.

if add code make sure add @ least on item each collection page display correctly.

the databinding done using c#, shown below.

xaml

            <phone:longlistselector grid.row="3" x:name="picturesgrid">                 <phone:longlistselector.itemtemplate>                     <datatemplate>                         <stackpanel orientation="horizontal" horizontalalignment="center">                             <image source="{binding filename}" />                         </stackpanel>                     </datatemplate>                 </phone:longlistselector.itemtemplate>             </phone:longlistselector> 

c#

      picturesgrid.itemssource = app.viewmodel.selectedbird.pictures; 

update: have noticed there scrollbar present, scroll never down bottom.