Fix seed boolean null handling #3879

Job	Run time
changes	5s
test-dbt-versions (1.4)	1m 32s
test-dbt-versions (1.7)	1m 53s
test-dbt-versions (1.5)	1m 33s
test-dbt-versions (1.8)	1m 43s
test-dbt-versions (1.9)	1m 49s
test-dbt-versions (1.10)	1m 57s
test-dbt-versions (1.6)	1m 34s
test-dbt-versions (1.3)	1m 48s
test-vscode	0s
test-vscode-e2e	0s
migration-test	1m 33s
cicd-tests-windows	11m 53s
doc-tests	30s
style-and-cicd-tests (3.12)	25m 34s
style-and-cicd-tests (3.13)	21m 54s
style-and-cicd-tests (3.11)	24m 2s
style-and-cicd-tests (3.9)	22m 17s
style-and-cicd-tests (3.10)	23m 42s
engine-tests-docker (duckdb)	1m 46s
engine-tests-docker (postgres)	2m 28s
engine-tests-docker (trino)	8m 50s
engine-tests-docker (mysql)	1m 43s
engine-tests-docker (mssql)	2m 31s
engine-tests-docker (risingwave)	2m 41s
engine-tests-docker (clickhouse)	2m 36s
engine-tests-docker (spark)	5m 15s
engine-tests-docker (starrocks)	3m 11s
ui-test	0s
ui-style	0s
engine-tests-cloud	0s
	2h 56m 20s

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