fix return from void (#549) #553

Job	Run time
ubuntu-latest\|debug\|--enable-mcsat\|CC=gcc CXX=g++	9m 14s
ubuntu-latest\|debug\|--enable-mcsat\|CC=clang CXX=clang++	10m 2s
ubuntu-latest\|debug\|--enable-thread-safety\|CC=gcc CXX=g++	4m 44s
ubuntu-latest\|debug\|--enable-thread-safety\|CC=clang CXX=clang++	5m 17s
ubuntu-latest\|release\|--enable-mcsat\|CC=gcc CXX=g++	6m 7s
ubuntu-latest\|release\|--enable-mcsat\|CC=clang CXX=clang++	6m 31s
ubuntu-latest\|release\|--enable-thread-safety\|CC=gcc CXX=g++	3m 10s
ubuntu-latest\|release\|--enable-thread-safety\|CC=clang CXX=clang++	3m 21s
ubuntu-latest\|gcov\|--enable-mcsat\|CC=gcc CXX=g++	8m 57s
ubuntu-latest\|debug\|--enable-thread-safety --enable-mcsat\|CC=gcc CXX=g++	8m 55s
	1h 6m 18s

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