Add "dont-test-empty" flag to bookmarks window/panel for tree speed optimization, as well as fix bug with empty folders.

xpfe/components/bookmarks/resources/bm-panel.xul

@@ -48,8 +48,7 @@
 </popupset>
 
     <tree id="bookmarksTree" class="bookmarks-panel-tree" context="contextual" ref="NC:BookmarksRoot"
-      flex="1"
-      multiple="true"
+      flex="1" multiple="true" flags="dont-test-empty"
       ondragover="return DragOverTree(event);"
       ondraggesture="return BeginDragTree(event);"
       ondragdrop="return DropOnTree(event);"

xpfe/components/bookmarks/resources/bookmarks.xul

@@ -184,7 +184,7 @@
 
 <tree  id="bookmarksTree" ref="NC:BookmarksRoot" context="contextual"
        datasources="rdf:bookmarks rdf:files rdf:localsearch rdf:internetsearch rdf:httpindex"
-       multiple="true"
+       multiple="true" flags="dont-test-empty"
        onselect="bookmarkSelect();"
        ondragover="return DragOverTree(event);"
        ondraggesture="return BeginDragTree(event);"