If I had handled that flag, I would have certainly converted it to a comment.
Restarting an application is the first thing to do whenever something goes wrong. It's troubleshooting 101 and as an answer it is way too generic. It's the type of "answer" you can put below every problem with an application and it will never be "wrong", because it's the reasonable first thing to try.
In case of this particular question restarting worked for the OP giving the answer but it didn't work for the OP asking the question. This shows how generic that "solution" is because sometimes it works and sometimes it doesn't. And that's why it should be a comment only.
We expect answers to contain factual information about how to solve specific problems. If restarting makes the error go away, it's a magic fix. You are lucky then. But it offers no insight whatsoever into the problem or why the solution works.
Likewise, because "restart your application" is so basic and generic as a "solution" it offers no value whatsoever to future visitors. It's so obvious to try that it doesn't qualify as an answer.
As a rule of thumb: if you dont know what exactly solves a problem but want to make suggestions about what to try, provide them as a comment an if that then turns out to solve the problem, turn it into an answer.
To add some numbers to illustrate that answering "restart your application" is not considered an answer, consider the following 5 posts (you need 10k to view these):
That's five out of many more deleted posts suggesting to restart the application: