Offset 'impression_data' does not exist on array{name: string, enabled: bool, variant: array{name: string, enabled: bool, payload?: array{type: string, value: string}}, impression_data?: bool, impressionData?: bool}.

Method Unleash\Client\Repository\DefaultUnleashProxyRepository::validateResponse() should return array{name: string, enabled: bool, variant: array{name: string, enabled: bool, payload?: array{type: string, value: string}}, impression_data?: bool, impressionData?: bool}|null but returns array<string, mixed>.