FIX: Modify frozen String and profile_db_generator uses category id (#8080)

script/profile_db_generator.rb

@@ -35,7 +35,7 @@ def sentence
     gabbler.learn(story)
   end
 
-  sentence = ""
+  sentence = +""
   until sentence.length > 800 do
     sentence << @gabbler.sentence
     sentence << "\n"
@@ -104,7 +104,7 @@ puts
 puts "Creating 100 topics"
 
 topic_ids = 100.times.map do
-  post = PostCreator.create(users.sample, raw: sentence, title: sentence[0..50].strip, category:  categories.sample.name, skip_validations: true)
+  post = PostCreator.create(users.sample, raw: sentence, title: sentence[0..50].strip, category:  categories.sample.id, skip_validations: true)
 
   putc "."
   post.topic_id