Fix assertion failure in LockFile::LockFile()
Fix assertion failure in LockFile::LockFile()

Fixes #4241.

rycee/nix,NixOS/nix,rycee/nix,NixOS/nix,rycee/nix,NixOS/nix,rycee/nix,NixOS/nix,rycee/nix,NixOS/nix