[devhelp] DhLink: fix get_book_name() if called on book top-level link

[Sébastien Wilmet <swilmet src gnome org>]

commit b6d225c14ea91c0c59f3ef1e413756de4b8703db
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Thu Dec 7 16:38:43 2017 +0100

    DhLink: fix get_book_name() if called on book top-level link
    
    dh_link_get_book_name() is now implemented similarly than
    dh_link_get_book_id().
    
    dh_link_get_book_name() is used only in dh-assistant-view.c and the
    change is OK there.

 src/dh-link.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/dh-link.c b/src/dh-link.c
index 2e54d0a..3149392 100644
--- a/src/dh-link.c
+++ b/src/dh-link.c
@@ -403,6 +403,9 @@ dh_link_get_book_name (DhLink *link)
 {
         g_return_val_if_fail (link != NULL, NULL);
 
+        if (link->type == DH_LINK_TYPE_BOOK)
+                return link->name;
+
         if (link->book != NULL)
                 return link->book->name;