The bug is with the new "clickable link" for /locate included in the snapshot 18w08b. This link automatically sets the Y value to 0.0, which, in effect, means that you will end up in the void upon executing the command. You can trigger this bug by using /locate for, I believe, any feature, then clicking the autoteleport link in chat. Screenshots are attached, the order of events is:
I hope that this has been useful!