Fix null comparison in Fido.ps1

[Zigler21]

This pull request fixes the null comparison issue in the Fido.ps1 file. The comparison was incorrectly written as $winVersionId -eq $null, and it has been corrected to $null -eq $winVersionId. This ensures that the comparison is done correctly and resolves the issue.

[pbatard]

Please describe the actual issue, with an error that can be replicated, because as far as I know, $A -eq $B vs $B -eq $A is a matter of personal preferences. All the $winXXX have been initialized to $null at the beginning of the function, so I currently fail to see what issue this PR is trying to address...

[Hrxn]

It works in both ways, but the PR is kind of right, because there's a potential pitfall in PowerShell.

https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_comparison_operators?view=powershell-7.4#equality-operators

• When the left-hand side is scalar, -eq returns True if the right-hand side is equivalent, otherwise, -eq returns False. -ne does the opposite; it returns False when both sides are equivalent; otherwise, -ne returns True.
• When the left-hand side is a collection, -eq returns those members that match the right-hand side, while -ne filters them out.

That explains the difference in functionality of LHS vs RHS.
The potential pitfall is if the LHS is unexpectedly a collection.

There is a rule in PSScriptAnalyzer about this.

Doc page of this rule, PossibleIncorrectComparisonWithNull.

I quote from this page:

To ensure that PowerShell performs comparisons correctly, the $null element should be on the left side of the operator.

There are multiple reasons why this occurs:

• $null is a scalar value. When the value on the left side of an operator is a scalar, comparison operators return a Boolean value. When the value is a collection, the comparison operators return any matching values or an empty array if there are no matches in the collection.
• PowerShell performs type casting left to right, resulting in incorrect comparisons when $null is cast to other scalar types.

The only way to reliably check if a value is $null is to place $null on the left side of the operator so that a scalar comparison is performed.