Fix crashes in tests #555

Job	Run time
ubuntu-latest\|debug\|--enable-mcsat\|CC=gcc CXX=g++	9m 5s
ubuntu-latest\|debug\|--enable-mcsat\|CC=clang CXX=clang++	9m 47s
ubuntu-latest\|debug\|--enable-thread-safety\|CC=gcc CXX=g++	4m 25s
ubuntu-latest\|debug\|--enable-thread-safety\|CC=clang CXX=clang++	4m 54s
ubuntu-latest\|release\|--enable-mcsat\|CC=gcc CXX=g++	6m 0s
ubuntu-latest\|release\|--enable-mcsat\|CC=clang CXX=clang++	6m 21s
ubuntu-latest\|release\|--enable-thread-safety\|CC=gcc CXX=g++	3m 26s
ubuntu-latest\|release\|--enable-thread-safety\|CC=clang CXX=clang++	3m 23s
ubuntu-latest\|gcov\|--enable-mcsat\|CC=gcc CXX=g++	8m 54s
ubuntu-latest\|debug\|--enable-thread-safety --enable-mcsat\|CC=gcc CXX=g++	9m 11s
	1h 5m 26s

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