Fix font not found errors on PPC Mac

No idea why this didn’t fail on other architectures, it was brain dead
broken since ce08d99.
[cppcheck] Redundant null check

[XeTeXFontMgr.cpp:201]: (error) Possible null pointer dereference: font
- otherwise it is redundant to check if font is null at line 208
[cppcheck] [XeTeX_ext.c:2114]: (error) Uninitialized variable: i
Clean this #ifdef nest to make the intent clear