fix(dsi): clamp browse pages to available results

Prevent invalid page numbers from producing empty, out-of-range menus.

hatenadir/ds/v2-xx/allflipnotes.ugo.py

@@ -1,13 +1,13 @@
 from twisted.web import resource
 from DB import Database
-from reximemo import dsi_url, flipnote_buttons, make_menu, pagination_buttons, query_int
+from reximemo import dsi_url, flipnote_buttons, make_menu, pagination_buttons, page_number
 
 
 class PyResource(resource.Resource):
     isLeaf = True
     def render_GET(self, request):
-        page = query_int(request, "page", 1)
         total = Database.count_flipnotes()
+        page = page_number(request, total)
         rows = Database.list_flipnotes(page=page, per_page=50)
         pager = pagination_buttons(request, "allflipnotes.uls", page, total)
         prev = [b for b in pager if b["label"].startswith("Previous")]