[PATCH 2/2] Fail more gracefully in bookmark functions if we get passed a null.

The new (at least) man parsing code obviously has a bug where it's not
setting a page_id that it should. But this shouldn't cause a segfault!
---
 src/yelp-application.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/src/yelp-application.c b/src/yelp-application.c
index 0921d16..cae00dd 100644
--- a/src/yelp-application.c
+++ b/src/yelp-application.c
 <at>  <at>  -674,6 +674,9  <at>  <at>  yelp_application_remove_bookmark (YelpBookmarks     *bookmarks,
     GSettings *settings;
     YelpApplication *app = YELP_APPLICATION (bookmarks);

+    g_return_if_fail (page_id);
+    g_return_if_fail (doc_uri);
+
     settings = application_get_doc_settings (app, doc_uri);

     if (settings) {
 <at>  <at>  -704,6 +707,9  <at>  <at>  yelp_application_is_bookmarked (YelpBookmarks     *bookmarks,
     GSettings *settings;
     YelpApplication *app = YELP_APPLICATION (bookmarks);

+    g_return_if_fail (page_id);
+    g_return_if_fail (doc_uri);
+
     settings = application_get_doc_settings (app, doc_uri);
     if (settings == NULL)
         return FALSE;