fix scan_build NULL error #952

Job	Run time
Check upstream code is properly integrated	1m 14s
Check code formatting	1m 10s
Check that code passes a basic build before starting heavier tests	1m 22s
linux_arm_emulated (armhf, armhf, -DOQS_ENABLE_SIG_SPHINCS=OFF -DOQS_USE_OPENSSL=OFF -DOQS_OPT_TA...	40m 55s
linux_intel (alpine, openquantumsafe/ci-alpine-amd64:latest, -DOQS_STRICT_WARNINGS=ON -DOQS_USE_O...	10m 54s
linux_intel (alpine-openssl-all, openquantumsafe/ci-alpine-amd64:latest, -DOQS_STRICT_WARNINGS=ON...	17m 20s
linux_intel (alpine-noopenssl, openquantumsafe/ci-alpine-amd64:latest, -DOQS_STRICT_WARNINGS=ON -...	11m 22s
linux_intel (focal-nistr4-openssl, openquantumsafe/ci-ubuntu-focal-x86_64:latest, -DOQS_STRICT_WA...	5m 7s
linux_intel (jammy-std-openssl3, openquantumsafe/ci-ubuntu-jammy:latest, -DOQS_STRICT_WARNINGS=ON...	4m 43s
linux_intel (address-sanitizer, openquantumsafe/ci-ubuntu-focal-x86_64:latest, -DCMAKE_C_COMPILER...	15m 38s
	1h 49m 45s

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