GCP | disks.list method returning error when ran as part of a script

Question

I am running this from PowerShell with gcloud CLI installed on my local Windows machine.

If I run disks.list by itself as followed, I get the expected output.

gcloud compute disks list `
    --project=prj-d-jenkins-poc `
    --filter="-users:*" `
    --format="csv(name,sizeGb,zone,status,type,lastAttachTimestamp,lastDetachTimestamp)"

If I run it as part of a script, I get an error.

Script:

#Initiated OUTPUT variable as ArrayList to collect results
$OUTPUT =  New-Object -TypeName "System.Collections.ArrayList"
$OUTPUT.Add("name,sizeGb,zone,status,type,lastAttachTimestamp,lastDetachTimestamp")

#Get list of accessible projects to PROJECTS
$PROJECTS = gcloud projects list --format="value(projectId)"

#Iterate through projects list 
foreach ($i in $PROJECTS)
{
    #Get list of unattached disks 
    $list = gcloud compute disks list `
    --project=$i `
    --filter="-users:*" `
    --format="csv(name,sizeGb,zone,status,type,lastAttachTimestamp,lastDetachTimestamp)"
    
    #If list is not empty, add it to OUTPUT
    if ($list.count -gt 0){
        $list = [System.Collections.ArrayList]$list #Convert a to ArrayList
        $list.RemoveAt($list.0) #Remove first entry for a
    
        $OUTPUT += $list #append a to OUTPUT
    
        Write-Host "Unattached disks in $i wrote to OUTPUT variable."
    }
    else{ #If list is empty, skip
        Write-Host "No unattached disks found in $i."
    }

}

$OUTPUT

Error I get sometimes as it iterates through the project list:

python.exe : WARNING: The following filter keys were not present in any resource : users
At C:\Users\minh.tran\AppData\Local\Google\Cloud SDK\google-cloud-sdk\bin\gcloud.ps1:117 char:3
+   & "$cloudsdk_python" $run_args_array
+   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (WARNING: The fo...esource : users:String) [], RemoteException
    + FullyQualifiedErrorId : NativeCommandError

I think this is because it was iterating through projects where there was no unattached disks, and that threw the error.

How do I modify my code so it will ignore these projects without unattached disks?