avahi: patch segfault on resolving .local addresses

Avahi would segfault on a NULL pointer dereference when trying to
resolve .local addresses.

This patch fixes that quite annoying behaviour, but apparently wasn’t
worth a release yet.

pkgs/development/libraries/avahi/default.nix

@@ -33,6 +33,10 @@ stdenv.mkDerivation rec {
 
   patches = [
     ./no-mkdir-localstatedir.patch
+    (fetchpatch {
+      url = "https://github.com/lathiat/avahi/commit/9d31939e55280a733d930b15ac9e4dda4497680c.patch";
+      sha256 = "sha256-BXWmrLWUvDxKPoIPRFBpMS3T4gijRw0J+rndp6iDybU=";
+    })
   ];
 
   buildInputs = [ libdaemon dbus glib expat libiconv libevent ]