Coverity: fix more null derefs #4681

Job	Run time
build library (--enable-intelasm --enable-sp-asm --enable-experimental --enable-kyber=yes,origina...	41s
build library (--disable-asm)	29s
build library (--enable-intelasm --enable-sp-asm)	37s
build library (--disable-asm --enable-all-crypto --enable-experimental --enable-kyber=yes,origina...	1m 0s
build library (--disable-asm --enable-experimental --enable-kyber=yes,original --enable-lms --ena...	47s
build library (--enable-intelasm --enable-sp-asm --enable-all-crypto --enable-experimental --enab...	59s
	4m 33s

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