Whenever I review Low Quality Posts (or any other posts), I see an "Edit" button. When I click on that button I'm able to edit the post even if there's a proposed edit pending. When the post is edited from queue it automatically rejects the pending edit as "This edit conflicted with a subsequent edit.".
For example, this post was in Low Quality Posts Queue. Then Eliah Kagan clicked on the "Edit" button, submitted and edit from there, and the pending suggested edit was rejected automatically. I discussed this with Eliah in chat and I think that it's a bug.
I think the review page should check if there's pending edit or not or at least redirect to "Suggested Edit" page if there's any. Since in my opinion, this wastes the time and efforts of <2000 reputation users and it may happen that the editor made better improvement than the reviewer.