Fix typo that could cause an infinite loop when tunnelling.
Fix typo that could cause an infinite loop when tunnelling.

Thanks to xnoreq for the extensive debugging session.

galeksandrp/polipo,TierraDelFuego/opilop,berkley4/polipo,akkakks/polipo,fqtools/polipo,berkley4/polipo,Psiphon-Inc/polipo,lkraider/polipo,nxtreaming/chumen,lkraider/polipo,nxtreaming/chumen,feijilei/polipo,akkakks/polipo,nxtreaming/chumen,berkley4/polipo,galeksandrp/polipo,jech/polipo,galeksandrp/polipo,jech/polipo,fqtools/polipo,akkakks/polipo,dxq-git/polipo,dxq-git/polipo,jech/polipo,ajmgh/polipo,ssb22/polipo2,dxq-git/polipo,ssb22/polipo2,fqtools/polipo,feijilei/polipo,ssb22/polipo2,clowwindy/polipo,lkraider/polipo,feijilei/polipo