Fix cross-engine CI compatibility

[elpete]

Fixes the two regressions introduced by the internal closure refactor:

• avoid shadowing the entity argument in QuickBuilder, which Adobe CF rejects
• do not dereference a null optional directConstraint on Lucee 5 or BoxLang

Local verification:

• Adobe 2021 QuickCollectionSpec: 3 passed
• Lucee 5 full-null QueryingRelationshipsSpec: 48 passed
• BoxLang 1 full-null QueryingRelationshipsSpec: 48 passed
• CFFormat and git diff --check passed