[CT-1541] Regression in logic for "selection criterion ... does not match any nodes"

[jtcohen6]

Petit regression in the main branch, introduced by #6064

Caught by Sung in #6271 (comment), and Mila in Slack

Before

dbt-core/core/dbt/graph/selector.py

Lines 145 to 146 in 8145eed

	if spec.expect_exists:
	alert_non_existence(spec.raw, direct_nodes)

dbt-core/core/dbt/graph/selector.py

Lines 27 to 29 in 8145eed

	def alert_non_existence(raw_spec, nodes):
	if len(nodes) == 0:
	warn_or_error(f"The selection criterion '{str(raw_spec)}' does not match any nodes")

After

dbt-core/core/dbt/graph/selector.py

Lines 139 to 140 in 9877648

	if spec.expect_exists:
	warn_or_error(NoNodesForSelectionCriteria(spec_raw=str(spec.raw)))

(missing the check for len(direct_nodes) == 0!)