Generated internals of external specialisations only if the template has template fields.

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

src/Generator/Passes/TrimSpecializationsPass.cs

@@ -134,6 +134,7 @@ namespace CppSharp.Passes
                 template.Specializations.All(s => s.Ignore))
                 template.ExplicitlyIgnore();
 
+            if (template.Fields.Any(f => f.Type.Desugar() is TemplateParameterType))
                 MoveExternalSpecializations(template);
         }