Multiple dropdown configuration issue

Hi all,

I'm going crazy about this: I want a multiple dropdown be populated by a d query on a data store:

local!config: a!queryEntity(
entity:local!dse[ri!dse],
query: a!query(
aggregation: a!queryAggregation(
aggregationColumns: {
a!queryAggregationColumn(field: ri!fieldName, isGrouping: true)
}
),
pagingInfo: a!pagingInfo(startIndex: 1, batchSize: - 1)
),
fetchTotalCount: false
).data[ri!fieldname],

and this is my dropdown configuration:

a!multipleDropdownField(
data:null,
placeholder:"null",
choiceValues:local!config,
choiceLabels:local!config,
label: "",
labelPosition: "ABOVE",
value: ri!value,
saveinto: ri!value,
searchDisplay: "AUTO",
marginBelow: "NONE"
)

but in test display it generate this error:

Could not display interface. Please check definition and inputs. Interface Definition: Expression evaluation error at function a!multipleDropdownField [line 4]: A multiple dropdown component [label="Multiple Dropdown"] has an invalid value for "choiceValues". Choice values cannot be null.

but on the right side of my screen I can see that the config variable is correctly populated.

Can anyone help me, please?

Maria Giuseppina