Mono: Fix '!t' error messages when generating bindings

This error wasn't affecting the bindings generation process.

modules/mono/editor/bindings_generator.cpp

@@ -730,7 +730,7 @@ Error BindingsGenerator::_generate_cs_type(const TypeInterface &itype, const Str
 	}
 
 	output.push_back(INDENT1 "public ");
-	bool is_abstract = !ClassDB::can_instance(itype.name) && ClassDB::is_class_enabled(itype.name); // can_instance returns true if there's a constructor and the class is not 'disabled'
+	bool is_abstract = itype.is_object_type && !ClassDB::can_instance(itype.name) && ClassDB::is_class_enabled(itype.name); // can_instance returns true if there's a constructor and the class is not 'disabled'
 	output.push_back(itype.is_singleton ? "static class " : (is_abstract ? "abstract class " : "class "));
 	output.push_back(itype.proxy_name);