Description:
LibreOffice got support for optional OpenType feature since 5.3, but if a font have intergrated both OT and Graphite features, some of OpenType features failed to work.

Steps to Reproduce:
Test with Duolos SIL
1. New Writer document
2. Enter some text, e.g. "ff, ffi, ff"
3. Change font for paragraph to "Duolos SIL"
4. Select text and add the ":liga=0" OT switch to the font list entry

Test with Ponomar Unicode TT (http://sci.ponomar.net/fonts.html)
1. Enter some text, e.g. "У, Є"
2. Change font for paragraph to "Ponomar Unicode TT"
3. Select text and add the ":salt=1" OT switch to the font list entry
4. Enter text "The quick brown fox."
5. Select text and add the ":ss02=1" OT switch to the font list entry


Actual Results:  
Standard ligature failed to work when I use Duolos SIL, also, stylistic alternates and stylistic set #2 failed to work with Ponomar Unoicode TT.

Expected Results:
If a intergrated both OT and Graphite features, both of them should works proper.


Reproducible: Always

User Profile Reset: No

Additional Info:
Version: 5.3.0.2 (x64)
Build ID: 5ad7b2889021c491af62f7930a4b1cb631392f16
CPU Threads: 4; OS Version: Windows 6.19; UI Render: default; 布局引擎：新; 
Locale: zh-CN (zh_CN); Calc: group

Documentation for Ponomar Unicode TT is available here: http://www.ponomar.net/files/fonts-churchslavonic.pdf


User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:51.0) Gecko/20100101 Firefox/51.0