Fix NRE in AssignmentNotUsedInspection

The inspection did not consider that the context on module declarations is always null. Now, member variables are ignored because the inspection is rather targeted at local variables.

Author: MDoerner

Rubberduck.CodeAnalysis/CodePathAnalysis/Walker.cs

@@ -5,7 +5,6 @@
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
-using Antlr4.Runtime;
 
 namespace Rubberduck.Inspections.CodePathAnalysis
 {

Rubberduck.CodeAnalysis/Inspections/Concrete/AssignmentNotUsedInspection.cs

@@ -6,6 +6,7 @@
 using Rubberduck.Parsing.Symbols;
 using Rubberduck.Inspections.CodePathAnalysis.Extensions;
 using System.Linq;
+using Rubberduck.Inspections.CodePathAnalysis.Nodes;
 using Rubberduck.Inspections.Results;
 using Rubberduck.Parsing;
 using Rubberduck.Parsing.Grammar;
@@ -30,7 +31,15 @@ protected override IEnumerable<IInspectionResult> DoGetInspectionResults()
             var nodes = new List<IdentifierReference>();
             foreach (var variable in variables)
             {
-                var tree = _walker.GenerateTree(variable.ParentScopeDeclaration.Context, variable);
+                var parentScopeDeclaration = variable.ParentScopeDeclaration;
+
+                if (parentScopeDeclaration.DeclarationType.HasFlag(DeclarationType.Module))
+                {
+                    continue;
+                }
+
+                var tree = _walker.GenerateTree(parentScopeDeclaration.Context, variable);
+
 
                 nodes.AddRange(tree.GetIdentifierReferences());
             }