Dropdown null value issue

Hi ,

I have an issue with dropdown. I want to display current year by default in my year dropdown.

For that i have appended year with the year dataset but its giving me error.

/*placeholderLabel: "--Select a Year-- ",*/ - In this by default current year should be display and selected.

Below code i have in load().

local!year1: append(tointeger(todatasubset(
    local!data,
    a!pagingInfo(
      startIndex: 1,
      batchSize: - 1,
      sort: a!sortInfo(
        field: "year",
        ascending: false
      )
    )
  ),year(today()))),
  local!year: if(
    rule!APN_isBlank(
      local!data
    ),
    {},
   union(
      index(
        local!year1.data,
        "year"
      ),
      index(
        local!year1.data,
        "year"
      )
      
    )
  ),

a!dropdownField(
label: "Year",
labelPosition: "ABOVE",
/*placeholderLabel: "--Select a Year-- ",*/
choiceLabels: local!Year,
choiceValues: local!Year,
value: local!selectedYear,
saveInto: { local!selectedCycleYear }
)

But i am getting error. Could not display interface. Please check definition and inputs.
Interface Definition: Expression evaluation error at function a!dropdownField [line 190]: A dropdown component [label=Year”] has an invalid value for “value”. Value cannot be null.

If i un comment this section - /*placeholderLabel: "--Select a Year-- ",*/ 

than its working fine but as per my requirement i don't want to display this text , dropdown should populate with year data along with current year on top of that(In selected mode)

What could be the workaround of this problem.