fix(frontends/lean/elaborator): bug when creating error message
fix(frontends/lean/elaborator): bug when creating error message

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