Invalid code crashes enu on open
On Edit mode, type something invalid on a block like a typo or something:

```nim
import grid
forward 3
INVALID
```

- Press <kbd> ESC </kbd>
- Enu closes.
- Open Enu again.
- Enu crashes.

```console
$ ./enu
error: undeclared identifier: 'invalid'
/home/juan/.local/share/enu/default/scripts/grid_14.nim done.
undeclared identifier: 'invalid'
segfaults.nim(76)        segfaultHandler
Error: unhandled exception: Could not access value because it is nil. [NilAccessDefect]

$
```
