[epiphany] bookmarks-popover: fix build error

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 06ecf1454d135ec857019d99b1f8e30a0a64c66c
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Mon Jan 23 21:45:00 2017 -0600

    bookmarks-popover: fix build error
    
    I was too overconfident when copy/pasting.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=772131

 src/bookmarks/ephy-bookmarks-popover.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/src/bookmarks/ephy-bookmarks-popover.c b/src/bookmarks/ephy-bookmarks-popover.c
index 56053d3..7f75dc1 100644
--- a/src/bookmarks/ephy-bookmarks-popover.c
+++ b/src/bookmarks/ephy-bookmarks-popover.c
@@ -74,6 +74,7 @@ ephy_bookmarks_popover_bookmark_tag_added_cb (EphyBookmarksPopover *popover,
   if (g_sequence_get_length (ephy_bookmark_get_tags (bookmark)) == 1) {
     GList *children;
     GList *l;
+    const char *visible_stack_child;
 
     children = gtk_container_get_children (GTK_CONTAINER (popover->tags_list_box));
     for (l = children; l != NULL; l = l->next) {
@@ -87,6 +88,7 @@ ephy_bookmarks_popover_bookmark_tag_added_cb (EphyBookmarksPopover *popover,
     /* If we are on the tag detail list box, then the user has toggled the state
      * of the tag widget multiple times. The first time the bookmark was removed
      * from the list box. Now we have to add it back. */
+    visible_stack_child = gtk_stack_get_visible_child_name (GTK_STACK (popover->toplevel_stack));
     if (g_strcmp0 (visible_stack_child, "tag_detail") == 0) {
       GtkWidget *row;
       row = create_bookmark_row (bookmark, popover);