hiddenfield shows on orientation change

[guardianchem]

steps to reproduce, on iphone 3gs:

add hiddenfield to formpanel

set hiddenfields value via code and go back to formpanel
formpanel.getComponent('myhiddenval').setValue(formpanel2.getComponent('myvisibleval').getValue());
mainpanel.setActiveItem(0);

finally, change orientation twice, hiddenfield now shows as a textfield.