Adjust CatchClauseOnlyRethrows to work with C#

[Laurens-W]

What's changed?

Take into account a possible J.Empty expression for a throws statement

Anyone you would like to review specifically?

@OlegDokuka @knutwannheden @timtebeek

Any additional context

In C# an implicit throw like this

catch (Exception ex)
{
    throw;
}

is valid code and it's mapped to a J.Empty expression

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files

[timtebeek]

Approved after my changes; but the one question about that J.Empty remains.