Async 1.9.3 not working with elgrep in emacs -Q

[TobiasZawada]

Elgrep with Emacs 26.1 and option -Q causes problems with async 1.9.3 (recursive search).

I get the error:

apply: Wrong type argument: stringp, nil

Workaround:

1. Deactivation of async
2. Running Emacs without option ´-Q`