When there is an issue with a clear bug report that can be fixed in on of two lines and the solution is very clear, I like to answer something like:

"Thanks for the report! The problem is in link-to-file-in-GitHub. Do you want to send a PR to fix it? If not, we can fix it."

Sometimes they accept the proposal, sometimes not. It is a little more work to fetch the change, rebase, and merge it. But some people like the opportunity and perhaps may become a contributor in the future.

(If they don't accept, fix the problem soon and say thanks again with a link to the fix in case they want to see the change.)