[v0.10] When two characters are ligatured, the first one becomes invisible

[xa0082249956]

Environment

Platform ServicePack Version      VersionString
-------- ----------- -------      -------------
 Win32NT             10.0.19582.0 Microsoft Windows NT 10.0.19582.0

Steps to reproduce

1. Change font to the one with ligatures, for example Fira Code.
2. Type --.

Expected behavior

The first - shouldn't disappear.

Actual behavior

The first - is disappeared.

[DHowett-MSFT]

What font size are you using? What version of Terminal?

[xa0082249956]

What font size are you using?

Default size i.e. 12.

What version of Terminal?

Windows Terminal (Preview)
Version: 0.10.761.0
Downloaded from Microsoft Store.

[onekopaka]

I am also having this issue, using 10pt Fira Code, no matter the zoom level, I just built from commit c0d704e

Here you can see the //, :: and www ligatures drawing incorrectly:

[DHowett-MSFT]

We thought we'd fixed this with #4806, but perhaps we didn't.