solution to useless button 4 and 5 in safari

{
                        "description": "useful button 4 and 5 in safari",
                        "manipulators": [
                            {
                                "conditions": [
                                    {
                                        "bundle_identifiers": [
                                            "com.apple.Safari"
                                        ],
                                        "type": "frontmost_application_if"
                                    }
                                ],
                                "from": {
                                    "modifiers": {
                                        "optional": [
                                            "caps_lock"
                                        ]
                                    },
                                    "pointing_button": "button5"
                                },
                                "to": [
                                    {
                                        "key_code": "close_bracket",
                                        "lazy": false,
                                        "modifiers": [
                                            "right_gui"
                                        ],
                                        "repeat": true
                                    }
                                ],
                                "type": "basic"
                            },
                            {
                                "conditions": [
                                    {
                                        "bundle_identifiers": [
                                            "com.apple.Safari"
                                        ],
                                        "type": "frontmost_application_if"
                                    }
                                ],
                                "from": {
                                    "modifiers": {
                                        "optional": [
                                            "caps_lock"
                                        ]
                                    },
                                    "pointing_button": "button4"
                                },
                                "to": [
                                    {
                                        "key_code": "open_bracket",
                                        "modifiers": [
                                            "right_gui"
                                        ],
                                        "repeat": true
                                    }
                                ],
                                "type": "basic"
                            }
                        ]
                    }