What's the point of writing a blank reply?

I also have the experience of replying to other people's blank letters, but I really don't know what to say, because I am full of feelings. If I have something, I want to say it, but I can't. If you have to say something, but you can't say it, your heart is very contradictory. However, if it is an empty message on your mobile phone, there are two situations. One is that I intentionally send you an empty message to show that I miss you but I don't know where to start, and the other is that I accidentally sent it when I pressed the button ~