empty nameref issue

[Léa Gris]

This is ok as here:

> # declare nameref without assigned value
> declare -n ref
>
> # use nameref as iterator
> for ref in foo bar baz
> do ref='Hello the World!'
> done
>
> declare -p foo bar baz

although: declare -n ref
leaves the ref variable in a limbo state with no value

> $ unset -n ref; declare -n ref; printf %q\\n "$ref"
> ''

This strangely cause no error and returns an empty string.

> $ unset -n ref; declare -n ref; printf %q\\n "${!ref}"
> bash: ref: invalid indirect expansion

But trying to expand the value of the nameref itself causes this 
"invalid indirect expansion error"

This seems counter-intuitive.
Intuitively:
- Expanding the value of a nameref without an assigned value should 
return an empty string.
- Expanding the value of the refered variable whose nameref is undefined 
would return some error

The other related issue is that this limbo empty state of a nameref is 
only obtained with an initial `declare -n ref`.
There is no way to later clear or assign an empty string to a nameref 
unless destroying and recreating the nameref with:

> unset -n ref
> declare -n ref



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Léa Gris