Remove empty tuple from SExp #1500

Job	Run time
Checks	1m 20s
Wheel on macos-latest py-3.7	3m 54s
Wheel on ubuntu-latest py-3.7	4m 36s
Wheel on windows-latest py-3.7	3m 35s
coverage	26m 40s
Run fuzz targets (macos-latest, 3.7)	42m 11s
Run fuzz targets (ubuntu-latest, 3.7)	27m 39s
Unit tests (macos-latest, 3.7)	7m 57s
Unit tests (ubuntu-latest, 3.7)	5m 59s
Unit tests (windows-latest, 3.7)	9m 33s
	2h 13m 24s

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