Interface Error

This is the process model i am adding the data in the first form and then generating the file using ms word and then in the User input task i want to download that document so i have given document download link to download that document. Everthing is working fine even the process variables is also taking data and generated document but the interface is given error.

{
a!sectionLayout(
contents: {
a!cardLayout(
showBorder: false,
contents: {
a!richTextDisplayField(
align: "CENTER",
value: {
a!richTextItem(
text: concat(
"We have shared your ticket on your Email.",
char(10),
"You can also click on "
),
style: "STRONG",
size: "LARGE",
color: ""
),
a!richTextItem(
text: "Download Ticket",
style: "STRONG",
size: "LARGE",
color: "NEGATIVE",
link: a!documentDownloadLink(
document: ri!document
)
)
}
)
}
)
}
)
}