fix(library/simplifier): compilation warning
fix(library/simplifier): compilation warning

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

soonhokong/lean-osx,soonhokong/lean,fgdorais/lean,htzh/lean,avigad/lean,johoelzl/lean,c-cube/lean,soonhokong/travis_test,dselsam/lean,soonhokong/lean-windows,digama0/lean,avigad/lean,soonhokong/lean-osx,htzh/lean,sp3ctum/lean,johoelzl/lean,soonhokong/lean,sp3ctum/lean,fgdorais/lean,Kha/lean,leanprover/lean,c-cube/lean,fpvandoorn/lean,Kha/lean,fpvandoorn/lean,javra/lean,htzh/lean,fpvandoorn/lean,soonhokong/lean-windows,fgdorais/lean,soonhokong/travis_test,rlewis1988/lean,soonhokong/lean-osx,johoelzl/lean,dselsam/lean,UlrikBuchholtz/lean,soonhokong/lean-windows,fpvandoorn/lean2,soonhokong/lean,eigengrau/lean,fgdorais/lean,soonhokong/lean-windows,fpvandoorn/lean2,dselsam/lean,soonhokong/lean,dselsam/lean,codyroux/lean0.1,levnach/lean,soonhokong/travis_test,leanprover/lean,Kha/lean,leodemoura/lean,codyroux/lean0.1,leanprover-community/lean,htzh/lean,Kha/lean,levnach/lean,codyroux/lean0.1,digama0/lean,fpvandoorn/lean,UlrikBuchholtz/lean,leanprover-community/lean,dselsam/lean,Kha/lean,c-cube/lean,rlewis1988/lean,codyroux/lean0.1,UlrikBuchholtz/lean,leanprover/lean,soonhokong/lean-windows,johoelzl/lean,htzh/lean,levnach/lean,digama0/lean,fpvandoorn/lean,javra/lean,avigad/lean,avigad/lean,fgdorais/lean,fgdorais/lean,rlewis1988/lean,dselsam/lean,fpvandoorn/lean2,leanprover/lean,johoelzl/lean,leodemoura/lean,johoelzl/lean,leanprover/lean,sp3ctum/lean,leanprover-community/lean,UlrikBuchholtz/lean,leanprover/lean,soonhokong/lean,javra/lean,sp3ctum/lean,eigengrau/lean,leodemoura/lean,leanprover-community/lean,avigad/lean,soonhokong/lean-osx,digama0/lean,eigengrau/lean,fpvandoorn/lean2,javra/lean,rlewis1988/lean,rlewis1988/lean,leodemoura/lean,soonhokong/travis_test,c-cube/lean,levnach/lean,avigad/lean,leanprover-community/lean,digama0/lean,leodemoura/lean,rlewis1988/lean,c-cube/lean,eigengrau/lean,Kha/lean,fpvandoorn/lean2,UlrikBuchholtz/lean,levnach/lean,javra/lean,digama0/lean,soonhokong/lean-osx,eigengrau/lean,leodemoura/lean,leanprover-community/lean,sp3ctum/lean,fpvandoorn/lean