Generate valid C# for classes with dependent fields nested in templates with independent fields

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

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -333,7 +333,7 @@ namespace CppSharp.Generators.CSharp
             foreach (var specialization in generated.KeepSingleAllPointersSpecialization())
                 GenerateClassInternals(specialization);
 
-            foreach (var group in generated.SelectMany(s => s.Classes).Where(
+            foreach (var group in specializations.SelectMany(s => s.Classes).Where(
                 c => !c.IsIncomplete).GroupBy(c => c.Name))
             {
                 var nested = classTemplate.Classes.FirstOrDefault(c => c.Name == group.Key);

tests/CSharp/CSharpTemplates.h

@@ -85,6 +85,11 @@ class IndependentFields : public T1
 {
     typedef T Type;
 public:
+    class Nested
+    {
+    private:
+        T field;
+    };
     IndependentFields();
     IndependentFields(const IndependentFields<T>& other);
     IndependentFields(const T& t);