fix return from void #552

Job	Run time
ubuntu-latest\|debug\|--enable-mcsat\|CC=gcc CXX=g++	9m 2s
ubuntu-latest\|debug\|--enable-mcsat\|CC=clang CXX=clang++	10m 56s
ubuntu-latest\|debug\|--enable-thread-safety\|CC=gcc CXX=g++	4m 38s
ubuntu-latest\|debug\|--enable-thread-safety\|CC=clang CXX=clang++	4m 59s
ubuntu-latest\|release\|--enable-mcsat\|CC=gcc CXX=g++	6m 7s
ubuntu-latest\|release\|--enable-mcsat\|CC=clang CXX=clang++	6m 34s
ubuntu-latest\|release\|--enable-thread-safety\|CC=gcc CXX=g++	3m 16s
ubuntu-latest\|release\|--enable-thread-safety\|CC=clang CXX=clang++	3m 26s
ubuntu-latest\|gcov\|--enable-mcsat\|CC=gcc CXX=g++	8m 51s
ubuntu-latest\|debug\|--enable-thread-safety --enable-mcsat\|CC=gcc CXX=g++	8m 54s
	1h 6m 43s

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