Invoke-DbaDbUpgrade - can't pass in more than one db at a time

[jpomfret]

Before submitting a bug report:

• Ensure you are able to reproduce it on the latest released version (we release often)
• Verified this bug is not already reported in an issue
• Verified errors are not related to permissions
• Can reproduce in a clean PowerShell session (clean = powershell -NoProfile)
• If issue is with Copy-DbaDatabase, using Backup-DbaDatabase | Restore-DbaDatabase still does not work

Note that we do not have the resources to make Copy-DbaDatabase work in every environment. Instead, we try to ensure Backup & Restore work in your enviornment.

Steps to Reproduce

Invoke-DbaDbUpgrade -SqlInstance $server -Database database1, database2 -NoCheckDb
## or 
Invoke-DbaDbUpgrade -SqlInstance $server -Database $($dbs.name) -NoCheckDb

Expected Behavior

I would expect the DbUpgrade to run against each database.

Actual Behavior

Command doesn't run against any databases.

Environmental data

• PowerShell:
  Name Value
  PSVersion 5.1.14393.2636
  PSEdition Desktop
  PSCompatibleVersions {1.0, 2.0, 3.0, 4.0...}
  BuildVersion 10.0.14393.2636
  CLRVersion 4.0.30319.42000
  WSManStackVersion 3.0
  PSRemotingProtocolVersion 2.3
  SerializationVersion 1.1.0.1

• SQL Server:
  Microsoft SQL Server 2017 (RTM-CU11) (KB4462262) - 14.0.3038.14 (X64) Sep 14 2018 13:53:44 Copyright (C) 2017 Microsoft Corporation Developer Edition (64-bit) on Windows Server 2016 Standard 10.0 (Build 14393: ) (Hypervisor)