nl_tokens: private - used by TabPanel too . Works out the next tab to activate when one tab is closed .
pl_tokens: function ( toClose ) { var me = this ; if ( toClose . <mask> && me . items . getCount ( ) > 1 ) { return ( me . previousTab && me . previousTab !== toClose && ! me . previousTab . disabled ) ? me . previousTab : ( toClose . next ( 'tab[disabled=false]' ) || toClose . prev ( 'tab[disabled=false]' ) ) ; } }