SqlSetup: Throws and obscure error message when installing Reporting Services without service account

Details of the scenario you try and problem that is occurring:
When installing a standalone Reporting Service and not providing a service account for Reporting Service service the setup throws and error that is hard to understand why it failed. Looking at the Bootstrap log you will see that it needs an account.
This could have been tested in the resource so that an error message can be thrown before starting the setup.

The DSC configuration that is using the resource (as detailed as possible):

xSQLServerSetup InstallSql2008R2Instance
{
    InstanceName = '2008R2'
    Features = 'RS'
    #RSSvcAccount = $SqlServiceCredential

    SetupCredential = $SqlInstallCredential
            
    SourcePath = $Node.SourcePath
    SourceFolder = $Node.SourceFolderSql2008R2
    SourceCredential = $SqlInstallCredential

    SuppressReboot = $False
    ForceReboot = $False

    DependsOn = '[WindowsFeature]NetFramework35','[WindowsFeature]NetFramework45'
}

Version of the Operating System, SQL Server and PowerShell the DSC Target Node is running:
OS: Windows Server 2012 R2
SQL Server: 2008 R2
PS: 5.0

Version of the DSC module you're using, or 'dev' if you're using current dev branch:
Dev

Start with the xSQLServerSetup resource and reproduce the standalone Reporting Services configuration shown in the issue, with RSSvcAccount omitted. Compare the resource behavior with the Bootstrap log; done means the resource reports a clear missing-account error before setup begins. No source file or test path is identified in the issue.