Get-Command fails with unexpected error when given a blank command-name argument #13342

Note: This is definitely a minor bug that won't arise too often in the real world.

Passing an all-whitespace -Name argument to Get-Command results in unexpected error message Get-Command: Index was outside the bounds of the array.

Steps to reproduce

{ Get-Command -ea Stop -Name ' '  } | Should -Throw -ErrorId CommandNotFoundException

Expected behavior

The test should succeed; that is, the usual CommandNotFoundException should be reported.

Actual behavior

The test fails, because the error mentioned above is reported instead.

Expected an exception, with FullyQualifiedErrorId 'CommandNotFoundException' to be thrown, 
but the FullyQualifiedErrorId was 
'System.IndexOutOfRangeException,Microsoft.PowerShell.Commands.GetCommandCommand'

Environment data

PowerShell Core 7.1.0-preview.5