Auto merge of #16388 - Tiwalun:fix-freetype-panic, r=emilio

Fix panic when font face name is not available

I got a panic in Servo when I ran it with `RUST_LOG=debug`, which was due to `FT_Get_Postscript_Name` returning a null pointer.

I'm not sure how to add a test for this, so there is none right now.

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