pkgs/microvm-command: don't break -l on nix eval error

Author: astro

pkgs/microvm-command.nix

@@ -168,7 +168,7 @@ writeScriptBin "microvm" ''
             NEW_SYSTEM=$(readlink "$DIR/toplevel")
           else
             FLAKE=$(cat "$DIR/flake")
-            NEW_SYSTEM=$(nix --option narinfo-cache-negative-ttl 10 eval --raw "$FLAKE#nixosConfigurations.$NAME.config.system.build.toplevel")
+            NEW_SYSTEM=$(nix --option narinfo-cache-negative-ttl 10 eval --raw "$FLAKE#nixosConfigurations.$NAME.config.system.build.toplevel" || echo error)
           fi
           NEW=''${NEW_SYSTEM#*-}