Fix issue in Verify-Link.ps1 after PS 7.4 update (#7623)

https://learn.microsoft.com/en-us/powershell/scripting/whats-new/what-s-new-in-powershell-74?view=powershell-7.4
- Add AllowInsecureRedirect switch to Web cmdlets (#18546)

That new option cause a new exception type that exposed
a bug where we assumed if InnerException property existed
that it was not null. This fix verifies that the property
is not null.

eng/common/scripts/Verify-Links.ps1

@@ -260,7 +260,7 @@ function CheckLink ([System.Uri]$linkUri, $allowRetry=$true)
         $innerExceptionPresent = $_.Exception.psobject.Properties.name -contains "InnerException"
 
         $errorCodePresent = $false
-        if ($innerExceptionPresent) {
+        if ($innerExceptionPresent -and $_.Exception.InnerException) {
           $errorCodePresent = $_.Exception.InnerException.psobject.Properties.name -contains "ErrorCode"
         }