Fixed the generated C# when a type nested in a template is forwarded.

Signed-off-by: Dimitar Dobrev <dpldobrev@protonmail.com>

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -270,7 +270,8 @@ namespace CppSharp.Generators.CSharp
             foreach (var specialization in generated)
                 GenerateClassInternals(specialization);
 
-            foreach (var group in generated.SelectMany(s => s.Classes).GroupBy(c => c.Name))
+            foreach (var group in generated.SelectMany(s => s.Classes).Where(
+                c => !c.IsIncomplete).GroupBy(c => c.Name))
                 GenerateNestedInternals(group.Key, group);
 
             WriteCloseBraceIndent();

tests/CSharp/CSharpTemplates.h

@@ -113,8 +113,10 @@ template <typename T>
 class DLL_API DependentValueFields : public Base<T>
 {
 public:
+    class Nested;
     class Nested
     {
+        T field;
     };
     DependentValueFields();
     ~DependentValueFields();
@@ -530,4 +532,4 @@ public:
 };
 
 class SpecializationOfClassWithNonTypeTemplateArgument : public ClassWithNonTypeTemplateArgument<0>
-{ };
+{ };