Powershell: Get-Date -UFormat '' throws an unhelpful exception for an empty string argument

An empty string argument in Get-Date -UFormat '' throws IndexOutOfRangeException, it would be more helpful if the error said what was wrong and directed attention to the UFormat argument. "Missing or Invalid UFormat String" or words to that effect.

Steps to reproduce

PS /test> get-date -uformat "$accidentallyEmptyFormatStringVariable"
get-date : Index was outside the bounds of the array.
At line:1 char:1
+ get-date -uformat ''
+ ~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Get-Date], IndexOutOfRangeException
    + FullyQualifiedErrorId : System.IndexOutOfRangeException,Microsoft.PowerShell.Commands.GetDateCommand

Expected behavior

A message directing attention to the -UFormat string parameter being empty.

Actual behavior

A message about some internal problem.

Environment data

> $PSVersionTable
Name                           Value
----                           -----
PSVersion                      6.0.0-beta.8
PSEdition                      Core
GitCommitId                    v6.0.0-beta.8
OS                             Linux 2.6.32-042stab120.6 #1 SMP Thu Oct 27 16:59:03 MSK 2016
Platform                       Unix
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0