[base] Improve error handling in `FT_GlyphLoader_CheckPoints`.

If `FT_GlyphLoader_CreateExtra` returns an error (and a couple of other
places), `FT_GlyphLoader_CheckPoints` would propagate the error immediately,
rather than cleaning up the partially set up `FT_GlyphLoader`.  As a
consequence, a subsequent attempt to create a glyph could result in a crash.

* src/base/ftgloadr.c (FT_GlyphLoader_CheckPoints): Ensure all the error
conditions exits are consistent, eventually calling `FT_GlyphLoader_Reset`.
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