Getting Error:Expression evaluation error at function fn!content_appian_internal [line 35]: Invalid Content ID

Hi,I am facing an issue where I am getting 
Expression evaluation error at function a!forEach [line 44]: Error in a!forEach() expression during iteration 1: Expression evaluation error in rule 'es_copy_ucaa_cmpt_fileupload' at function a!fileUploadField [line 27]: Error in a!forEach() expression during iteration 1: Expression evaluation error at function fn!content_appian_internal [line 35]: Invalid Content ID.please help me to resolve this issue

a!fileUploadField(
label: ri!label,
labelPosition: if(
a!defaultValue(ri!showLabel, true),
null,
"COLLAPSED"
),
helpTooltip: ri!helpTooltip,
target: ri!folderId,
value: index(ri!documents, "appianDocId", null),
saveInto: {
a!save(
ri!documents,
a!forEach(
items: tointeger(save!value),
expression: a!update(
data: cast(
'type!{urn:com:appian:types:PRI}PRI_Document',
rule!GBL_indexWhere(
value: fv!item,
initialArray: index(ri!documents, "appianDocId", {}),
finalArray: ri!documents
)
),
index: {
"appianDocId",
"questionAttribute",
"questionName",
"documentIdentifier"
},
value: {
fv!item,
ri!questionAttribute,
ri!questionName,
ri!identifier
}
)
)
)
},
required: ri!isRequired,
requiredMessage: ri!requiredMessage,
buttonDisplay: "ICON",
maxSelections: ri!maxDocuments
)