- this PR should close#9596
- fixes#9596
- this PR should close#9826
- fixes#9826
fixed the following bugs:
```nu
# type following statements in the nushell
let f = 'f' $;
mut f = 'f' $;
const f = 'f' $;
# then remove variable f, it will panics
let = 'f' $;
mut = 'f' $;
const = 'f' $;
```