fix(library/unifier): bugs exposed by recent changes
fix(library/unifier): bugs exposed by recent changes

Signed-off-by: Leonardo de Moura <7610bae85f2b530654cc716772f1fe653373e892@microsoft.com>

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