In 06e06939 (encoder: Allow to specify pickle protocol version) I added
ability to add to tests error cases - object inputs that on encoding
should produce error.

For decoding we should skip those cases as there pickle.data = "", and
if not skipped it leads to

	--- FAIL: BenchmarkDecode
	    ogorek_test.go:803: unexpected # of decode steps: got 100  ; want 102