[XeTeX] Somes unicode letters

[Anas Ghrab]

Hello all,

Some unicode letters do not appear in my pdf file. I do not know why.  
For example :

miḏrāb

gives

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The letter ḏ is coded 1E0E in the unicode.

Thanks,

---
Anas Ghrab
http://anas.ghrab.org
http://www.saramusik.org