Fix S3928: Rule throws NullReferenceException

[antrv]

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
        }

        public void Method(IEnumerable<string> items)
        {
            foreach (var item in items)
            {
                switch (item)
                {
                    case "a":
                    {
                        break;
                    }

                    default:
                        throw new ArgumentOutOfRangeException(nameof(item), item, null);
                }
            }
        }
    }
}

When compiling the following simple console application, SonarAnalyzer.CSharp gives the exception:

AD0001	Analyzer 'SonarAnalyzer.Rules.CSharp.CheckArgumentException' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'.	ConsoleApp2		1	Active	Analyzer 'SonarAnalyzer.Rules.CSharp.CheckArgumentException' threw the following exception:
'Exception occurred with following context:
Compilation: ConsoleApp2
SyntaxTree: C:\Users\anton.ryzhov\Documents\Visual Studio 2017\Projects\ConsoleApp2\ConsoleApp2\Program.cs
SyntaxNode: new ArgumentOutOfRangeException ... [ObjectCreationExpressionSyntax]@[384..441) (18,22)-(18,79)
System.NullReferenceException: Object reference not set to an instance of an object.
   at SonarAnalyzer.Rules.CSharp.CheckArgumentException.TakeOnlyBeforeDot(Optional`1 value)
   at SonarAnalyzer.Rules.CSharp.CheckArgumentException.CheckForIssue(SyntaxNodeAnalysisContext analysisContext)
   at SonarAnalyzer.Helpers.DiagnosticAnalyzerContextHelper.<>c__DisplayClass0_0`1.<RegisterSyntaxNodeActionInNonGenerated>b__0(SyntaxNodeAnalysisContext c)
   at SonarAnalyzer.Helpers.SonarAnalysisContext.<>c__DisplayClass12_0`1.<RegisterSyntaxNodeAction>b__0(SyntaxNodeAnalysisContext c)
   at Microsoft.CodeAnalysis.Diagnostics.AnalyzerExecutor.<>c__43`1.<ExecuteSyntaxNodeAction>b__43_0(ValueTuple`2 data)
   at Microsoft.CodeAnalysis.Diagnostics.AnalyzerExecutor.ExecuteAndCatchIfThrows_NoLock[TArg](DiagnosticAnalyzer analyzer, Action`1 analyze, TArg argument, Nullable`1 info)

---

EDIT: I have changed the styling (@Evangelink)

[antrv]

Sorry for styling :)

[michalb-sonar]

Thanks for the report and good repro code @antrv. I was able to reproduce the problem, we'll fix it soon.