The small delete register "- doesn't work

[ShiruiQian]

Describe the bug
Charactars deleted by "nx" in one line shoud be stored in the small delete register "-.
But they are stored in the unnamed register "".

• Extension (VsCodeVim) version:1.0.8
• VSCode version:1.31.1
• OS:win7 64

[rickythefox]

For reference, from Vim docs:

3. Small delete register "-
   This register contains text from commands that delete less than one line,
   except when the command specifies a register with ["x].
   {not in Vi}