fix: only print comment if there's groups

Author: zaucy

rt_entt_codegen/core/create_registry.cc

@@ -17,13 +17,19 @@ auto ecsact::rt_entt_codegen::core::print_create_registry( //
 
 	ctx.write("auto&& [registry_id, reg] = ecsact::entt::create_registry();\n\n");
 
-	ctx.write(
-		"// These groups were automatically selected based on the input ecsact "
-		"files\n"
-	);
-	for(auto sys_id : details.group_systems) {
-		auto cpp_decl_name = cpp_identifier(ecsact::meta::decl_full_name(sys_id));
-		ctx.write("ecsact::entt::prepare_system_like<", cpp_decl_name, ">(reg);\n");
+	if(!details.group_systems.empty()) {
+		ctx.write(
+			"// These groups were automatically selected based on the input ecsact "
+			"files\n"
+		);
+		for(auto sys_id : details.group_systems) {
+			auto cpp_decl_name = cpp_identifier(ecsact::meta::decl_full_name(sys_id));
+			ctx.write(
+				"ecsact::entt::prepare_system_like<",
+				cpp_decl_name,
+				">(reg);\n"
+			);
+		}
 	}
 
 	ctx.write("\nreturn registry_id;");