fix(frontends/lean/scanner): assertion
fix(frontends/lean/scanner): assertion

leodemoura/lean,leodemoura/lean,rlewis1988/lean,johoelzl/lean,rlewis1988/lean,leanprover-community/lean,dselsam/lean,fpvandoorn/lean,dselsam/lean,leanprover/lean,digama0/lean,Kha/lean,Kha/lean,rlewis1988/lean,avigad/lean,leanprover/lean,Kha/lean,avigad/lean,avigad/lean,leanprover/lean,rlewis1988/lean,fpvandoorn/lean,fpvandoorn/lean,fpvandoorn/lean,johoelzl/lean,avigad/lean,digama0/lean,leanprover/lean,leanprover-community/lean,dselsam/lean,digama0/lean,digama0/lean,leanprover-community/lean,johoelzl/lean,dselsam/lean,leodemoura/lean,leanprover/lean,leodemoura/lean,fpvandoorn/lean,Kha/lean,dselsam/lean,leanprover-community/lean,Kha/lean,leanprover-community/lean,Kha/lean,leodemoura/lean,dselsam/lean,avigad/lean,leanprover/lean,leanprover-community/lean,fpvandoorn/lean,digama0/lean,digama0/lean,johoelzl/lean,rlewis1988/lean,johoelzl/lean,avigad/lean,rlewis1988/lean,johoelzl/lean,leodemoura/lean