fix(library/module_mgr): do not perform unnecessary copy
fix(library/module_mgr): do not perform unnecessary copy

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