             @$el.toggleClass "minimized", 100
 
         sortBy : (field, old_field) ->
+
+            return unless @collection?
 
             re = new RegExp(" (#{_.values(@sortArrows).join("|")})$|$")
             dir = @collection.sortingDirection[field] ? 1

            
            super options

            if @collection?
                @collection.on "selected deselected reset", @checkRequirements, this
                @view.on "keypressed", @keypressedOnView, this if @hotkey?

            @checkRequirements()
    
  
        checkRequirements: ->
            enable = @allowed()

            if @selectedByDefault is true 
                @$list.find(".item.selected").trigger "deselect", silent: true
                @selectedByDefault = false
                @collection?.trigger "deselected"
            else
                @$list.find(".item:not(.selected)").trigger "select", silent: true
                @selectedByDefault = true
                @collection?.trigger "selected"

        invertSelected : ->
            toSelect = @$list.find(":not(.item.selected)")
