CHIA-2281 Clarify transactions generator check in test_parser

[AmineKhaldi]

Both gen and block.transactions_generator are Optional.

[coveralls-official]

Pull Request Test Coverage Report for Build 13029511444

Details

• 3 of 4 (75.0%) changed or added relevant lines in 1 file are covered.
• 13 unchanged lines in 6 files lost coverage.
• Overall coverage increased (+0.004%) to 91.512%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
chia/_tests/util/test_full_block_utils.py	3	4	75.0%

Files with Coverage Reduction	New Missed Lines	%
chia/_tests/simulation/test_simulation.py	1	96.45%
chia/util/config.py	1	84.62%
chia/rpc/rpc_server.py	1	89.16%
chia/full_node/full_node.py	1	86.22%
chia/server/node_discovery.py	2	79.49%
chia/daemon/server.py	7	83.46%

Totals
Change from base Build 13019247618:	0.004%
Covered Lines:	105268
Relevant Lines:	114853

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💛 - Coveralls