html2canvas: html2canvas.js:373 Invalid value given for Length: "auto"

Error: html2canvas.js:373 Invalid value given for Length: "auto" and Error2: localhost:8080/#!/Reports:1 Uncaught (in promise) invalid image, images dictionary should contain dataURL entries (or local file paths in node.js)

my controller contains

  $scope.export = function() {
        html2canvas(document.getElementById('balanceSheet')).then(function (canvas) {
            document.body.appendChild(canvas);
            var data = canvas.toDataURL();
            var docDefinition = {
                content: [{
                    image: data,
                    width: 500,
                }]
            };
            pdfMake.createPdf(docDefinition).download("test.pdf");
        });
    }

I already imported pdfmake.min.js and html2canvas.js

any help here?