replace stub returns with redirects

app/routes/topics.py

@@ -51,7 +51,7 @@ def topic(slug):
         "slug": slug
     })
     if not target_topic:
-        return "no"
+        return redirect(url_for('.all_topics'))
 
     threads_count = Threads.count({
         "topic_id": target_topic.id
@@ -77,7 +77,7 @@ def topic(slug):
 def edit(slug):
     topic = Topics.find({"slug": slug})
     if not topic:
-        return "no"
+        return redirect(url_for('.all_topics'))
     return render_template("topics/edit.html", topic=topic)
 
 
@@ -87,7 +87,7 @@ def edit(slug):
 def edit_post(slug):
     topic = Topics.find({"slug": slug})
     if not topic:
-        return "no"
+        return redirect(url_for('.all_topics'))
 
     topic.update({
         "name": request.form.get('name', default = topic.name).strip(),
@@ -104,7 +104,7 @@ def edit_post(slug):
 def delete(slug):
     topic = Topics.find({"slug": slug})
     if not topic:
-        return "no"
+        return redirect(url_for('.all_topics'))
 
     topic.delete()