Fix binary_search_string and assert in test_api8 #554

Job	Run time
ubuntu-latest\|debug\|--enable-mcsat\|CC=gcc CXX=g++	9m 52s
ubuntu-latest\|debug\|--enable-mcsat\|CC=clang CXX=clang++	9m 37s
ubuntu-latest\|debug\|--enable-thread-safety\|CC=gcc CXX=g++	4m 36s
ubuntu-latest\|debug\|--enable-thread-safety\|CC=clang CXX=clang++	5m 18s
ubuntu-latest\|release\|--enable-mcsat\|CC=gcc CXX=g++	6m 2s
ubuntu-latest\|release\|--enable-mcsat\|CC=clang CXX=clang++	6m 32s
ubuntu-latest\|release\|--enable-thread-safety\|CC=gcc CXX=g++	3m 25s
ubuntu-latest\|release\|--enable-thread-safety\|CC=clang CXX=clang++	3m 35s
ubuntu-latest\|gcov\|--enable-mcsat\|CC=gcc CXX=g++	9m 39s
ubuntu-latest\|debug\|--enable-thread-safety --enable-mcsat\|CC=gcc CXX=g++	9m 14s
	1h 7m 50s

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