Problem:
The default unimpaired mappings display an empty line after the
command's output. This results (with default configuration) in the
`Press ENTER or type command to continue` prompt to be displayed, like
so:
```
(2 of 16): item2
Press ENTER or type command to continue
```
Solution:
The cause is that we're checking the second return value from
`pcall(vim.api.nvim_cmd, opts, {})` to determine whether the call was
successful. `nvim_cmd` returns an empty string on success, so this value
is an empty string in the successful path which we then display.
The fix is simple: check the first return value instead which is the
"status code" of the call.
Before calling "attach" a screen object is just a dummy container for
(row, col) values whose purpose is to be sent as part of the "attach"
function call anyway.
Just create the screen in an attached state directly. Keep the complete
(row, col, options) config together. It is still completely valid to
later detach and re-attach as needed, including to another session.
