Code that yields a "Cannot set property 'geometry' of undefined" error from Cesium

cesiumErrorCode.js

// Make JSON call to EPA streams layer to return stream vector geometry within the viewport
    Cesium.jsonp('http://watersgeo.epa.gov/arcgis/rest/services/NHDPlus_NP21/NHDSnapshot_NP21/MapServer/0/query',{
        parameters: {
            geometryType: "esriGeometryPolygon",
            geometry: geometry,
            outFields: 'COMID',
            inSR: '{"wkid" : 4326}',
            outSR: '{"wkid" : 4326}',
            f: 'json'
        }
    })
        .then(function(data) {
            viewer.entities.suspendEvents();
            var numFeatures = data.features.length;
            var selectedCOMIDS = [];
            plotCountBefore = plotCounter;
            plotCounter++;
            for (var i = 0; i < numFeatures; i++) {
                var entityCoords = [];
                var numCoordinates = data.features[i].geometry.paths[0].length;
                var coordinates = data.features[i].geometry.paths[0];
                for (var ii = 0; ii < numCoordinates; ii++) {
                    entityCoords.push(coordinates[ii][0]);
                    entityCoords.push(coordinates[ii][1]);
                }
                var comid = data.features[i].attributes.COMID;
                selectedCOMIDS.push(comid);
                selectedEntities.push(viewer.entities.add({
                    id: comid,
                    polyline: {
                        positions: Cesium.Cartesian3.fromDegreesArray(entityCoords),
                        width: 2,
                        material: Cesium.Color.YELLOW
                    }
                }));

                var midPoint = entityCoords.length / 2;
                var midIndex = midPoint % 2 == 0 ? midPoint : midPoint + 1;
                var selectionName = getSelectionName();
                var showLabels = $('#labels-toggle').bootstrapSwitch('state');
                selectedLabels.push(viewer.entities.add({
                    position: Cesium.Cartesian3.fromDegrees(entityCoords[midIndex], entityCoords[midIndex + 1]),
                    label: {
                        text: selectionName,
                        style: Cesium.LabelStyle.FILL_AND_OUTLINE,
                        outlineWidth: 2
                    },
                    id: (comid.toString() + "label"),
                    show: showLabels
                }));
            }
            viewer.entities.resumeEvents();
            get_netcdf_chart_data(selectedCOMIDS);
        })
}

function get_netcdf_chart_data(comids) {

    if (comids.constructor === Array) {
        comids = comids.join();
    }

    $.ajax({
        type: 'GET',
        url: 'get-netcdf-data',
        dataType: 'json',
        data: {'comids': comids },
        success: function (data) {
            if ("success" in data) {
                if ("return_data" in data) {
                    var chart_data = JSON.parse(data.return_data);
                    var seriesCount = chart_data.length;

                    viewer.entities.suspendEvents();

                    for (var i = 0; i < seriesCount; i++) {
                        for (var key in chart_data[i]) {
                            if (chart_data[i][key][0][1] == -9999) {
                                viewer.entities.removeById(key);
                                selectedEntities = $.grep(selectedEntities, function(e) {
                                    return (e._id != key);
                                });

                                viewer.entities.removeById(key.toString() + "label");
                                selectedLabels = $.grep(selectedLabels, function(e) {
                                    return (e._id != (key.toString() + "label"));
                                });
                            }
                        }
                    }
                    viewer.entities.resumeEvents();
                }
            }   
        }
    });
}