Fix next page btn appearing on empty blog search (#183)

Tumblr's internal API returns no data when no blog search results are
found. This includes the necessary blog info to render the
blog's header.

\#173 worked around this by instead requesting the main page of a blog
and then clearing the posts list as to simulate empty results. However,
it neglected to clear the next attribute which contains the data
required to fetch the next batch of content and is used by the frontend
to determine whether to render a next page button.

This oversight caused the frontend to display a next page button
incorrectly which will cause an error if a user attempts to
navigate to the next page.

src/routes/blogs/blogs.py

@@ -64,17 +64,19 @@ async def _blog_search(request: sanic.Request, blog: str, query: str):
         continuation = urllib.parse.unquote(continuation)
 
     try:
-        blog = (await get_blog_search_results(request.app.ctx, blog, query, continuation=continuation))
+        blog_timeline = (await get_blog_search_results(request.app.ctx, blog, query, continuation=continuation))
     except IndexError:
-        # When no search results are found blog information will also be missing
-        blog = await get_blog_posts(request.app.ctx, blog)
-        blog.posts.clear()
+        blog_timeline = priviblur_extractor.models.timelines.BlogTimeline(
+            blog_info=(await get_blog_posts(request.app.ctx, blog)).blog_info,
+            posts=[],
+            total_posts=0
+        )
 
     return await request.app.ctx.render(
         "blog/blog_search",
         context={
             "app": request.app,
-            "blog": blog,
+            "blog": blog_timeline,
             "blog_search_query": query,
         },
     )