Improve CheckIgnoredDecls.IsTypeExternal to deal with declarations with no namespaces.

src/Generator/Passes/CheckIgnoredDecls.cs

@@ -403,16 +403,22 @@ namespace CppSharp.Passes
         private bool IsTypeExternal(Module module, Type type)
         {
             Declaration declaration;
-            if ((type.GetFinalPointee() ?? type).TryGetDeclaration(out declaration))
-            {
+            if (!(type.GetFinalPointee() ?? type).TryGetDeclaration(out declaration))
+                return false;
+
             declaration = declaration.CompleteDeclaration ?? declaration;
+            if (declaration.Namespace == null || declaration.TranslationUnit.Module == null)
+                return false;
+
+            // Check if there’s another module which wraps libraries with dependencies on
+            // the ones in the current module.
             if (declaration.TranslationUnit.Module.Libraries.Any(l =>
                     Context.Symbols.Libraries.First(
                         lib => lib.FileName == l).Dependencies.Any(
                             d => module != declaration.TranslationUnit.Module &&
                                 module.Libraries.Contains(d))))
                 return true;
-            }
+
             return false;
         }