Attach active pane item view before showing/hiding

Fixes #4112

src/pane-element.coffee

@@ -94,16 +94,16 @@ class PaneElement extends HTMLElement
     hasFocus = @hasFocus()
     itemView = @model.getView(item)
 
+    unless @itemViews.contains(itemView)
+      @itemViews.appendChild(itemView)
+      callAttachHooks(itemView)
+
     for child in @itemViews.children
       if child is itemView
         @showItemView(child) if @attached
       else
         @hideItemView(child)
 
-    unless @itemViews.contains(itemView)
-      @itemViews.appendChild(itemView)
-      callAttachHooks(itemView)
-
     itemView.focus() if hasFocus
 
   showItemView: (itemView) ->