New issue by rnkn on mblaze repository

https://github.com/leahneukirchen/mblaze/issues/261

Description:
Hello,

mless appears to be off-by-one when issuing the `N:x` command.

## To reproduce

```
$ mlist Maildir/ | mless
2:n
1:x
```
And then
```
2:x
```

## Expected results

Navigation back to message 1.

## Actual results

First the error
```
mless scan// (message 1 of 6)
```
And then
```
mless 1 (message 2 of 6)
```