Editable grid is displaying unknown error for date and sum function?

a!localVariables(
local!projectdata:rule!totaltimesheet(),

local!projectid,

local!updateCounter: 0,
local!employee: a!refreshVariable(

refreshOnVarChange: local!updateCounter
),
{

a!dateField(
label: "Date",
labelPosition :"JUSTIFIED",
value: ri!timeline.taskdate,
saveInto:ri!timeline.taskdate,

),
a!sectionLayout(
label: "",
contents: {

a!gridLayout(
/*label: "Grid view of an employee Details",*/
labelPosition: "ABOVE",
totalCount: count(ri!timeline),
headerCells: {
/*a!gridLayoutHeaderCell(label: "Employee Name"),*/
a!gridLayoutHeaderCell(label: "Project Name"),
a!gridLayoutHeaderCell(label: "Task Name"),

a!gridLayoutHeaderCell(label: "Description"),
a!gridLayoutHeaderCell(label: "Hours"),

a!gridLayoutHeaderCell(label: "Status"),
a!gridLayoutHeaderCell(
label: ""
)

},
columnConfigs: {
/*a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight:2),*/
a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight:2),
a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight:2),

a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight:2),

a!gridLayoutColumnConfig(width: "DISTRIBUTE", weight:2),
a!gridLayoutColumnConfig(
width: "ICON"
)

},
rows: a!forEach(
items: ri!timeline,
expression:a!gridRowLayout(

contents: {
/*a!textField(*/
/* */
/*value: loggedInUser(),*/
/*saveInto: {fv!item.employerName, a!save(ri!timeline.employerName, save!value)},*/
/*refreshAfter: "UNFOCUS",*/
/*required: true,*/
/*readOnly: true */
/* */
/* */
/*),*/

a!dropdownField(
label: "project Name ",
placeholderLabel: " ",
choiceLabels: rule!CrochetDSR_Get_ProjectName().projectname,
choiceValues: rule!CrochetDSR_Get_ProjectName().projectid,
value: fv!item.projectid,
saveInto: fv!item.projectid,
required: true
),
/*a!dropdownField(*/
/*label: "task",*/
/*placeholderLabel: " ",*/
/*choiceLabels: rule!CrochetDSR_Get_MilestoneTaskName(projectid:local!projectid).taskname,*/
/*choiceValues: rule!CrochetDSR_Get_MilestoneTaskName(projectid:local!projectid).taskname,*/
/*value: fv!item.taskname,*/
/*saveInto: fv!item.taskname,*/
/* */
/*required: true*/
/*) ,*/
a!textField(
label: "Description ",
value: fv!item.taskname,
saveInto: fv!item.taskname,
required: true
),
a!textField(
label: "Description ",
value: fv!item.description,
saveInto: fv!item.description,
required: true
),
/*a!dateField(*/
/*label: "task date ",*/
/*value: fv!item.taskdate,*/
/*saveInto: fv!item.taskdate,*/
/*required: true */
/*),*/
a!textField(
label: "Hours ",
value: fv!item.noofhours,
saveInto: fv!item.noofhours,
required: true
),

a!dropdownField(
label: "Status ",
placeholderLabel: " ",
choiceLabels: {"Done","Pending"},
choiceValues: {"Done","Pending"},
value: fv!item.Status,
saveInto: fv!item.Status,
required: true
),
a!imageField(
label: "delete " & fv!index,
images: a!documentImage(
document: a!iconIndicator(
"REMOVE"
),
altText: "Remove",
link: a!dynamicLink(
value: fv!index,
saveInto: {
a!save(
ri!timeline,
remove(
ri!timeline,
save!value
)
)
}
)

)
)


}
)
),


/*selectionvalue: ri!selectedRowIndex,*/
/*selectionsaveinto: ri!selectedRowIndex,*/
/*selectable: true,*/
selectionrequired: false,
addRowLink: a!dynamicLink(
label: "Add Timesheet",
saveInto: {
a!save(
target: ri!timeline,
value: append(
ri!timeline,
'type!{urn:com:appian:types:DSR}DSR_TimeSheetLineItem'(
employerName: loggedInUser(),

)
)
)
}
),
height: "AUTO",
spacing: "DENSE",
borderstyle: "STANDARD",
rowHeader: 1



),

a!columnsLayout(
columns: {
a!columnLayout(
contents: {}
),
a!columnLayout(
contents: {}
),
a!columnLayout(
contents: {
a!textField(
label: "Total Hours ",
labelPosition :"ADJACENT",
value: sum(ri!timeline.noofhours),
saveInto: {ri!timeline.Totalhours, a!save(ri!timeline.Totalhours, save!value)},
readOnly: true
),

}
)
}
),



a!buttonLayout(
primaryButtons: {
a!buttonWidgetSubmit(
label: "Submit",
value: ri!timeline,
/*saveInto: {a!save(ri!timeline.timesheetid,ri!pid),*/
/*ri!submitbutton,*/
/*a!writeToDataStoreEntity(*/
/*dataStoreEntity: cons!CROCHETDSR_GET_TIMESHEET,*/
/*valueToStore: ri!timeline,*/
/*)*/
/**/
/*},*/
showWhen: if(
rule!APN_isEmpty1(
ri!timeline
),
false(),
true()
),
style: "PRIMARY",
confirmHeader: {
if(
rule!APN_isEmpty1(
ri!timeline
),
"Please add at least one row",
{}
)
},
confirmMessage: {
if(
rule!APN_isEmpty1(
ri!timeline
),
"Please add at least one row",
{}
)
}
)
},
secondaryButtons: {
a!buttonWidget(
label: "Cancel",
value: true,
saveInto: ri!cancel,
submit: true,
style: "NORMAL",
validate: false
)
}


)

}


),

}

)