That's in regards to one of your LW preferences settings, namely Autocompletion of text fields. In order to turn this off, go to LW's menu Tools-Options & View. Select Autocomplete & untick the box for enable.
I was just thinking, originally I had mine set to off & didn't learn about it until I hit this forum. Now that I've used it & learnt a few tricks about how to use it (such as searching material by the same artist), it saves me from continually pasting the search criteria in, which is what I used to do. Mind you, just a few mths ago I was still using LW2 & I couldn't even paste into the search. I found that very annoying. So I guess it's however it suits the particular person.