[Validator] Fix propertyPath with nested collections in the LegacyExecutionContext

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #11072
| License       | MIT
| Doc PR        | -

Some tests are failing for other reasons.

missing trailing comma