fix(emacs/lean-util): fix lean-path-list to only include existing dirs
fix(emacs/lean-util): fix lean-path-list to only include existing dirs

Fix #246

leanprover/lean,Kha/lean,avigad/lean,soonhokong/lean,soonhokong/lean-osx,fgdorais/lean,soonhokong/lean,johoelzl/lean,eigengrau/lean,fpvandoorn/lean2,digama0/lean,leanprover-community/lean,fpvandoorn/lean2,htzh/lean,fpvandoorn/lean2,leodemoura/lean,leanprover/lean,levnach/lean,fpvandoorn/lean2,javra/lean,c-cube/lean,Kha/lean,eigengrau/lean,soonhokong/lean-windows,sp3ctum/lean,soonhokong/lean-windows,c-cube/lean,eigengrau/lean,leodemoura/lean,johoelzl/lean,dselsam/lean,soonhokong/lean-osx,fpvandoorn/lean,leanprover/lean,c-cube/lean,soonhokong/lean-osx,rlewis1988/lean,dselsam/lean,avigad/lean,Kha/lean,fgdorais/lean,avigad/lean,soonhokong/lean,avigad/lean,leanprover-community/lean,UlrikBuchholtz/lean,javra/lean,dselsam/lean,soonhokong/lean-windows,fpvandoorn/lean,rlewis1988/lean,leodemoura/lean,htzh/lean,digama0/lean,eigengrau/lean,javra/lean,soonhokong/lean-windows,javra/lean,leanprover-community/lean,c-cube/lean,soonhokong/lean-osx,fgdorais/lean,leodemoura/lean,soonhokong/lean,leanprover/lean,johoelzl/lean,johoelzl/lean,leodemoura/lean,leodemoura/lean,dselsam/lean,levnach/lean,dselsam/lean,digama0/lean,fpvandoorn/lean,htzh/lean,digama0/lean,soonhokong/lean-windows,levnach/lean,htzh/lean,sp3ctum/lean,fpvandoorn/lean,eigengrau/lean,sp3ctum/lean,UlrikBuchholtz/lean,soonhokong/lean,rlewis1988/lean,sp3ctum/lean,dselsam/lean,fgdorais/lean,fgdorais/lean,digama0/lean,sp3ctum/lean,fgdorais/lean,Kha/lean,fpvandoorn/lean,rlewis1988/lean,javra/lean,rlewis1988/lean,leanprover/lean,avigad/lean,leanprover-community/lean,johoelzl/lean,johoelzl/lean,UlrikBuchholtz/lean,rlewis1988/lean,htzh/lean,leanprover-community/lean,levnach/lean,fpvandoorn/lean2,leanprover-community/lean,avigad/lean,levnach/lean,leanprover/lean,digama0/lean,fpvandoorn/lean,c-cube/lean,Kha/lean,UlrikBuchholtz/lean,UlrikBuchholtz/lean,Kha/lean,soonhokong/lean-osx