worksheet: fix resource leaks on error paths #186

Job	Run time
Cmake (gcc)	55s
Cmake (gcc, -DBUILD_EXAMPLES=ON -DBUILD_TESTS=ON)	59s
Cmake (gcc, -DUSE_DTOA_LIBRARY=ON -DBUILD_TESTS=ON)	58s
Cmake (gcc, -DUSE_MEM_FILE=ON -DBUILD_TESTS=ON)	56s
Cmake (gcc, -DUSE_NO_MD5=ON -DBUILD_TESTS=ON)	54s
Cmake (gcc, -DUSE_OPENSSL_MD5=ON -DBUILD_TESTS=ON)	1m 2s
Cmake (gcc, -DUSE_STANDARD_TMPFILE=ON -DBUILD_TESTS=ON)	55s
Cmake (gcc, -DUSE_SYSTEM_MINIZIP=ON -DBUILD_TESTS=ON)	56s
Cmake (gcc, -DUSE_SYSTEM_MINIZIP=ON -DUSE_OPENSSL_MD5=ON -DBUILD_TESTS=ON)	1m 16s
Cmake (clang)	1m 8s
Cmake (clang, -DBUILD_EXAMPLES=ON -DBUILD_TESTS=ON)	1m 8s
Cmake (clang, -DUSE_DTOA_LIBRARY=ON -DBUILD_TESTS=ON)	1m 5s
Cmake (clang, -DUSE_MEM_FILE=ON -DBUILD_TESTS=ON)	1m 16s
Cmake (clang, -DUSE_NO_MD5=ON -DBUILD_TESTS=ON)	1m 5s
Cmake (clang, -DUSE_OPENSSL_MD5=ON -DBUILD_TESTS=ON)	1m 42s
Cmake (clang, -DUSE_STANDARD_TMPFILE=ON -DBUILD_TESTS=ON)	1m 9s
Cmake (clang, -DUSE_SYSTEM_MINIZIP=ON -DBUILD_TESTS=ON)	1m 6s
Cmake (clang, -DUSE_SYSTEM_MINIZIP=ON -DUSE_OPENSSL_MD5=ON -DBUILD_TESTS=ON)	1m 9s
	19m 39s

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