[issue18408] Fixes crashes found by pyfailmalloc

[STINNER Victor]

STINNER Victor added the comment:

"fix CJK codecs: using UNIINV to report _PyUnicodeWriter_WriteChar() failure in Modules/cjkcodecs/cjkcodecs.h does not work. The caller is not aware of the failure: multibytecodec_decerror() receives e=1, whereas it should get MBERR_EXCEPTION"

I created the issue #18509 for that.

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue18408>
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