This could previously crash lix:
Before:
$ nix eval -E '{type="derivation"; drvPath="";}'
nix: lix/libutil/file-system.cc:45: Path nix::canonPath(PathView, bool): Assertion `path != ""' failed.
Aborted (core dumped)
After:
$ nix eval -E '{type="derivation"; drvPath="";}'
error:
… while evaluating the drvPath of a derivation
at «string»:1:21:
1| {type="derivation"; drvPath="";}
| ^
error: path '' is not in the Nix store
Fixes#536
Change-Id: I406dc9e58047be8f263cf2e4bc3ed5da75a46602
gilice
341e6049a7