Focus next pane when removing the last pane item of a focused pane

Previously, removing the last pane item also ruined our ability to 
determine if the pane had focus. Now, if we're removing the last item,
we instead just go ahead and remove the entire pane. Remove contains
logic to switch focus to the next pane if its active view is focused,
which works as intended if we leave the active view in place.

src/app/pane.coffee

@@ -105,10 +105,8 @@ class Pane extends View
 
     @showNextItem() if item is @activeItem and @items.length > 1
     _.remove(@items, item)
-
     @cleanupItemView(item)
     @trigger 'pane:item-removed', [item, index]
-    @remove() unless @items.length
 
   moveItem: (item, newIndex) ->
     oldIndex = @items.indexOf(item)
@@ -125,16 +123,20 @@ class Pane extends View
 
   cleanupItemView: (item) ->
     if item instanceof $
-      item.remove()
+      viewToRemove = item
     else
       viewClass = item.getViewClass()
       otherItemsForView = @items.filter (i) -> i.getViewClass?() is viewClass
       unless otherItemsForView.length
-        view = @viewsByClassName[viewClass.name]
-        view?.setModel(null)
-        view?.remove()
+        viewToRemove = @viewsByClassName[viewClass.name]
+        viewToRemove?.setModel(null)
         delete @viewsByClassName[viewClass.name]
 
+    if @items.length > 0
+      viewToRemove?.remove()
+    else
+      @remove()
+
   viewForItem: (item) ->
     if item instanceof $
       item
@@ -197,19 +199,24 @@ class Pane extends View
 
   remove: (selector, keepData) ->
     return super if keepData
+
     # find parent elements before removing from dom
     container = @getContainer()
     parentAxis = @parent('.row, .column')
+
     if @is(':has(:focus)')
-      rootView?.focus() unless container.focusNextPane()
+      container.focusNextPane() or rootView?.focus()
     else if @isActive()
       container.makeNextPaneActive()
 
     super
 
     if parentAxis.children().length == 1
-      sibling = parentAxis.children().detach()
+      sibling = parentAxis.children()
+      siblingFocused = sibling.is(':has(:focus)')
+      sibling.detach()
       parentAxis.replaceWith(sibling)
+      sibling.focus() if siblingFocused
     container.adjustPaneDimensions()
     container.trigger 'pane:removed', [this]