can't delete bookmarks in the toplevel folder

[vcap]

since commit 98c87e7c katze_item_get_meta_data_value() returns NULL for empty strings; but this breaks the deletion of bookmarks in the toplevel folder because midori_bookmarks_remove_item_cb() now generate a query of the form:

    DELETE FROM bookmarks WHERE uri = 'foo://bar.baz' AND folder = '(NULL)'

which won't match any row; while it previously did:

   DELETE FROM bookmarks WHERE uri = 'foo://bar.baz' AND folder = ''

which delete the correct row.

(note that the sidepanel make it look like the bookmark is deleted; but it really isn't, as shown by the bookmarks widget in the navigation bar; and if you restart midori, the bookmark will show up in the sidepanel again)

attached is a patch to midori_bookmarks_remove_item_cb() that make it treats a NULL value for folder as "" instead, reestablishing the old behaviour.

[vcap (vcappe)]

> since commit 98c87e7c katze_item_get_meta_data_value() returns NULL for

 katze_item_get_meta_string(), actually.

[Cris Dywan (kalikiana)]

I committed a modified patch, using katze_str_non_null (previously STR_NON_NULL). Thanks a lot for tracking this down.