I want to use [leaflet-groupedlayercontrol](https://github.com/ismyrnow/leaflet-groupedlayercontrol) plugin with empty "dummy" layer groups that are only used to enable or disable filters for the GeoJSON layer when selected/unselected in the layers control. But the markers don't appear on the map and with `groupCheckboxes = true` it also doesn't group the layers. How can I solve this?

Example GeoJSON:

    {
        "type": "FeatureCollection",
        "features": [
            {
                "type": "Feature",
                "geometry": {
                    "type": "Point",
                    "coordinates": [
                        -9.2574095,
                        38.7720292
                    ]
                },
                "properties": {
                    "state": "G",
                    "CCO": "16",
                    "PostM_8": "1",
                    "PostM_9": "0",
                    "PostM_10": "0",
                    "PostM_12": "0",
                    "PostB_8_450": "0",
                    "CVP ": "0",
                    "NR1_D400": "1",
                    "NR1_B125": "0",
                    "NR2_D400": "0",
                    "NR2_B125": "1",
                    "NR3_D400": "0",
                    "TM_State": "677,4"
                }
            },
            {
                "type": "Feature",
                "geometry": {
                    "type": "Point",
                    "coordinates": [
                        -9.250804,
                        38.75554135
                    ]
                },
                "properties": {
                    "state": "B",
                    "CCO": "14",
                    "PostM_8": "1",
                    "PostM_9": "0",
                    "PostM_10": "1",
                    "PostM_12": "0",
                    "PostB_8_450": "0",
                    "CVP ": "0",
                    "NR1_D400": "1",
                    "NR1_B125": "0",
                    "NR2_D400": "0",
                    "NR2_B125": "0",
                    "NR3_D400": "0",
                    "TM_State ": "1037,3"            }
            },
            {
                "type": "Feature",
                "geometry": {
                    "type": "Point",
                    "coordinates": [
                        -9.354285,
                        38.72788
                    ]
                },
                "properties": {
                    "state": "G",
                    "CCO": "14",
                    "PostM_8": "1",
                    "PostM_9": "1",
                    "PostM_10": "0",
                    "PostM_12": "0",
                    "PostB_8_450": "0",
                    "CVP ": "0",
                    "NR1_D400": "0",
                    "NR1_B125": "0",
                    "NR2_D400": "0",
                    "NR2_B125": "0",
                    "NR3_D400": "0",
                    "TM_State": "940,3"
                }
            }

JS:

    var map = L.map("map", {
        zoomControl: false,
        fullscreenControl: true,
        fullscreenControlOptions: {
            position: 'bottomright'
        }
    }).setView([38.851470, -9.268658], 11);
    
    L.control.zoom({
        position: 'bottomright'
    }).addTo(map);
    
    var osm = L.tileLayer("https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png",
        {
            maxZoom: 19,
            attribution:
                '&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors',
        })
    
    // google street
    googleStreets = L.tileLayer('http://{s}.google.com/vt/lyrs=m&x={x}&y={y}&z={z}', {
        maxZoom: 20,
        subdomains: ['mt0', 'mt1', 'mt2', 'mt3']
    });
    googleStreets.addTo(map);
    
    //google satellite
    googleSat = L.tileLayer('http://{s}.google.com/vt/lyrs=s&x={x}&y={y}&z={z}', {
        maxZoom: 20,
        subdomains: ['mt0', 'mt1', 'mt2', 'mt3']
    });
    
    
    var myIcon = L.icon({
        iconUrl: 'img/img_markers/red_marker.png',
        iconSize: [40, 40],
    });
    
    var selectCondition = [];
    var selectLayer = [];
    
    for (var i = 0; i < 12; i++) {
        selectCondition[i] = false;
        selectLayer[i] = L.layerGroup();
        selectLayer[i].myId = i;
    }
    
    var baseMaps = {
        "OSM": osm,
        'Google Street': googleStreets,
        "Google Satellite": googleSat,
    };
    
    
    var overlayMaps = {
        'Postes': {
            'PostM_8': selectLayer[0],
            'PostM_9': selectLayer[1],
            'PostM_10': selectLayer[2],
            'PostM_12': selectLayer[3],
            'PostB_8_450': selectLayer[4]
        },
        'CVP´s': {
            'CVP': selectLayer[5],
            'NR1_D400': selectLayer[6],
            'NR1_B125': selectLayer[7],
            'NR2_D400': selectLayer[8],
            'NR2_B125': selectLayer[9],
            'NR3_D400': selectLayer[10]
        },
        'Temp': {
            'TM_State': selectLayer[11]
        }
    };
    
    var options = {
        groupCheckboxes: true,
        collapsed: false
    };
    
    L.control.groupedLayers(baseMaps, overlayMaps, options}).addTo(map);
    
    var report = L.geoJSON(null, {
        filter: function(feature, layer) {
            var cond1 = ((feature.properties.PostM_8 == '1') && selectCondition[0]);
            var cond2 = ((feature.properties.PostM_9 == '1') && selectCondition[1]);
            var cond3 = ((feature.properties.PostM_10 == '1') && selectCondition[2]);
            var cond4 = ((feature.properties.PostM_12 == '1') && selectCondition[3]);
            var cond5 = ((feature.properties.PostB_8_450 == '1') && selectCondition[4]);
            var cond6 = ((feature.properties.CVP == '1') && selectCondition[5]);
            var cond7 = ((feature.properties.NR1_D400 == '1') && selectCondition[6]);
            var cond8 = ((feature.properties.NR1_B125 == '1') && selectCondition[7]);
            var cond9 = ((feature.properties.NR2_D400 == '1') && selectCondition[8]);
            var cond10 = ((feature.properties.NR2_B125 == '1') && selectCondition[9]);
            var cond11 = ((feature.properties.NR3_D400 == '1') && selectCondition[10]);
            var cond16 = ((feature.properties.TM_State >= '600') && selectCondition[11]);
            return (cond1 || cond2 || cond3 || cond4 || cond5 || cond6 || cond7 || cond8 || cond9 || cond10 || cond11);
        },
        pointToLayer: function (feature, latlng) {
            return new L.marker(latlng, {
                icon: myIcon, draggable: false});
        },
        onEachFeature: setPopup 
    });
    
    var geojsonData;
    var url = './markers/markers.json';
    fetch(url)
        .then(response => {
            return response.json();
        })
        .then(json => {
            geojsonData = json;
            map.addLayer(report);
            selectLayer[0].addTo(map);
        });
    
    map.on('overlayadd', function(evt) {
        var i = overlayMaps[evt.name].myId;
        selectCondition[i] = true;
        report.clearLayers();
        report.addData(geojsonData);
    });
    
    map.on('overlayremove', function(evt) {
        var i = overlayMaps[evt.name].myId;
        selectCondition[i] = false;
        report.clearLayers();
        report.addData(geojsonData);
    });