neovim.tests.nvim_with_opt_plugin: fixed

once :Dashboard succeeded, the script would close neovim and thus never
terminate. We instead check if the command ":Dashboard" exists.

pkgs/applications/editors/neovim/tests/default.nix

@@ -260,13 +260,12 @@ rec {
       packadd dashboard-nvim-unique-for-tests-please-dont-use-opt
 
       " Try to run Dashboard again, and throw if it fails
-      try
-        Dashboard
-        echo "Dashboard found"
-      catch /^Vim\%((\a\+)\)\=:E492/
+      let res = exists(':Dashboard')
+      if res == 0
         echo "Dashboard not found, throwing error"
         cquit 1
-      endtry
+      endif
+      cquit 0
     '';
   };