Fix possible NULL pointer dereference. #414

Job	Run time
coverity-test	0s
coverity-test	0s
coverity-test	0s
coverage-test	6m 59s
coverage-test	7m 5s
coverage-test	7m 16s
fuzzing-test	4m 34s
fuzzing-test	4m 40s
fuzzing-test	4m 36s
generic-build-test (ubuntu-18.04, gcc)	5m 30s
generic-build-test (ubuntu-18.04, gcc)	5m 25s
generic-build-test (ubuntu-18.04, gcc)	7m 5s
generic-build-test (ubuntu-18.04, clang)	5m 31s
generic-build-test (ubuntu-18.04, clang)	5m 26s
generic-build-test (ubuntu-18.04, clang)	6m 12s
generic-build-test (ubuntu-20.04, gcc)	2m 16s
generic-build-test (ubuntu-20.04, gcc)	5m 26s
generic-build-test (ubuntu-20.04, gcc)	6m 52s
generic-build-test (ubuntu-20.04, clang)	5m 33s
generic-build-test (ubuntu-20.04, clang)	5m 27s
generic-build-test (ubuntu-20.04, clang)	5m 58s
generic-build-test (fedora-30, gcc)	5m 34s
generic-build-test (fedora-30, gcc)	5m 27s
generic-build-test (fedora-30, gcc)	7m 18s
generic-build-test (fedora-30, clang)	5m 32s
generic-build-test (fedora-30, clang)	5m 28s
generic-build-test (fedora-30, clang)	6m 37s
generic-build-test (opensuse-leap, gcc)	5m 33s
generic-build-test (opensuse-leap, gcc)	5m 27s
generic-build-test (opensuse-leap, gcc)	6m 56s
generic-build-test (opensuse-leap, clang)	5m 14s
generic-build-test (opensuse-leap, clang)	5m 10s
generic-build-test (opensuse-leap, clang)	6m 12s
generic-build-test (ubuntu-22.04, gcc)	2m 13s
generic-build-test (ubuntu-22.04, gcc)	5m 28s
generic-build-test (ubuntu-22.04, gcc)	44m 42s
	3h 44m 42s

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