BRIGHTSCRIPT: ERROR: roSGNode.AddReplace: "url": Type mismatch: pkg:/components/home_scene.brs(62) f

I want to add timer to load my JSON file after every 5 sec but i'm getting this error. This is my code for selected category.

function loadFeed(url)
    ? "Change every 5 sec"
    ? "URL"url
    m.feed_task = CreateObject("roSGNode", "load_feed_task")
    m.feed_task.observeField("response", "onFeedResponse")

    m.feed_task.url = url
    m.feed_task.control = "RUN"
end function

function onFeedResponse(obj)
    response = obj.getData()
    ' turn the JSON string into an Associative Array
    fetch = ParseJson(response)
    tempStrechData = CreateObject("roArray", 0, true)
    m.global.addFields({ strechedData: [] })
    if fetch <> invalid and fetch.data <> invalid
        ' hide the category screen and show content screen
        m.category_screen.visible = false
        m.content_screen.visible = true
        ' assign data to content screen
        m.content_screen.feed_data = fetch

        tempStrechData.Push(fetch)
        ? tempStrechData
        m.global.strechedData = tempStrechData
        ? m.global.strechedData
    else
        ? "FEED RESPONSE IS EMPTY!"
    end if
end function

sub onCategorySelected(obj)
    ? "onCategorySelected field: "; obj.getField()
    ? "onCategorySelected data: "; obj.getData()
    list = m.category_screen.findNode("category_list")
    ? "onCategorySelected checkedItem: "; list.checkedItem
    ? "onCategorySelected selected ContentNode: "; list.content.getChild(obj.getData())
    item = list.content.getChild(obj.getData())

    m.global.AddField("url", "string", false)
    url = item.feed_url
    ' code for timer
    m.testtimer = m.top.findNode("testTimer")
    m.testtimer.control = "start"

    m.textchange = false

    m.testtimer.ObserveField("fire", "loadFeed")

    m.top.setFocus(true)
' code for timer
    ' loadFeed(url)

    ' loadFeed(item.feed_url)
end sub