Do you stop jungling and cover the lane to give up any map pressure?
Do you keep jungling and hope to god other lanes win faster than they push?
Do you just farm it up for the remaining 12 minutes and then surrender?
As a jg main I refuse to cover lane. So I just spent 400 gold on an item that is absolutely worthless in lane, and now i'm supposed to take a champ that usually has a terrible early game mid because someone disconnects. F*ck that.
When I have to occupy a lane because of an afk, I almost always give a kill to the enemy, usually because the person disconnected because he ragequit for first blood, meaning I am at a HUGE disadvantage (because a 
mid who bought a machete is expected to win lane vs a 1/0 LeBlanc, right?) and my team starts screaming at ME for ruining the game. Yep, you heard right. No one blames the person who spent the entire game AFK, but everyone is happy to spam report the jungler who tried to prevent the enemy from getting free farm.
I signed up for jungle, not mid. It's entirely his fault for leaving the game. Sorry but unless i'm in a premade where the people understand how difficult it is for a jg to cover lane AFTER machete is bought and won't report me, that lane is just going to have to rot.
I'm not changing my plans because someone else screwed up.
It's honestly a game to game scenario. If your lane has fed before they quit its probably not a good idea to cover it. Realistically at that point you won't be able to stop the snowball alone and you should focus on ganking another lane.
I've found that when someone DCs during laning phase I want to end laning as soon as possible and start letting my team roam before anyone snowballs off free farm and/or someone on your team falls behind from the extra gank pressure.
If your laner dc'd but was winning his lane pretty hard, I'd suggest continuing to punish that lane, take the tower and try to end laning phase asap. Especially if the enemy is behind. You need to win before they can get back into the game.
