fix: skip conditional errors if the installation is failing

Author: zimeg

scripts/install-windows.ps1

@@ -220,7 +220,7 @@ function terms_of_service {
     [string]$Alias
   )
   $confirmed_alias = check_slack_binary_exist $Alias $Version $true
-  if (Get-Command $confirmed_alias) {
+  if (Get-Command $confirmed_alias -ErrorAction SilentlyContinue) {
     Write-Host "`nUse of the Slack CLI should comply with the Slack API Terms of Service:"
     Write-Host "   https://slack.com/terms-of-service/api"
   }
@@ -232,7 +232,7 @@ function feedback_message {
     [string]$Alias
   )
   $confirmed_alias = check_slack_binary_exist $Alias $Version $false
-  if (Get-Command $confirmed_alias) {
+  if (Get-Command $confirmed_alias -ErrorAction SilentlyContinue) {
     Write-Host "`nWe would love to know how things are going. Really. All of it."
     Write-Host "   Survey your development experience with ``$confirmed_alias feedback``"
   }