Emplty Json payload error in calling graph api in powershell - microsoft-graph-api

Question

Below is the error and the code I have for uploading files in SharePoint Library. I am trying to upload it in a folder inside a document library. It works fine if I am uploading it in root level of library but gives below error while uploading it in a folder Releae342 inside a library. Any clue what is wrong here? This api do not require any JSON content
Code for upload:
Function GET-UPLOADLINK
{
param($clientId, $clientSecret, $artifactname)
$tokenObject = GET-TOKEN -clientId $clientId -clientSecret $clientSecret
$uploadLinkRequestHeaders = New-Object "System.Collections.Generic.Dictionary[[String],[String]]"
$uploadLinkRequestHeaders.Add("Content-Type", "application/json")
$uploadLinkRequestHeaders.Add("Authorization", "Bearer "+ $tokenObject.access_token)
$uploadLinkRequestBody = ""
$artifactname = "test"
$fullname = "https://graph.microsoft.com/v1.0/sites/$($SPid)/drives/$($LibId)/root:/Release342/"
$comname = $fullname + $artifactname
$uploadLinkResponse = Invoke-RestMethod "$($comname).zip/createUploadSession" -Method 'POST' -Headers $uploadLinkRequestHeaders -Body $uploadLinkRequestBody
$uploadLinkResponse | ConvertTo-Json
return $uploadLinkResponse
}
Error Received:
Invoke-RestMethod : {
2020-12-10T14:41:58.9122308Z "error": {
2020-12-10T14:41:58.9122643Z "code": "BadRequest",
2020-12-10T14:41:58.9123035Z "message": "Empty Payload. JSON content expected.",
2020-12-10T14:41:58.9124293Z "innerError": {
2020-12-10T14:41:58.9124899Z "date": "2020-12-10T14:41:58",
2020-12-10T14:41:58.9125415Z "request-id": "d58a3213-cb8c-4e95-aac2-a076d36f88d9",
2020-12-10T14:41:58.9125886Z "client-request-id": "d58a3213-cb8c-4e95-aac2-a076d36f88d9"
2020-12-10T14:41:58.9126535Z }
2020-12-10T14:41:58.9126848Z }