Bugfix: List Marker nuked on empty List Item

```
If I type "- " and then ENTER on a new line
Or "* "
It deletes the line
For a bonus, write "--" on a new line
Press enter, get -
Delete -
Then select the "-- " and the line below it, and press enter
(To delete the line)
```

Start by reproducing the listed typing and selection sequences in the Simplenote iOS editor, then trace the editor entry point that handles list markers and newline or deletion actions. Done means the reported empty-list-item cases no longer delete or unexpectedly alter the marker, with the existing behavior checked against each reproduction step.

Written by the indexing model from the issue text.