Fix double '/'

handler/api.js

@@ -122,7 +122,7 @@ var QRHandler = {
     getQR:function(tagName){
         let qrImgPath = '/'+tagName+'.png';
         if(!FILE.exists(QRPATH+qrImgPath)){
-            let qr = new QR({value:SystemURL+'/'+tagName});
+            let qr = new QR({value:SystemURL+tagName});
             let qrData = qr.toDataURL().replace(/^data:image\/\w+;base64,/, "");
             FILE.writeFileSync(QRPATH+qrImgPath,new Buffer(qrData, 'base64'),'binary');
         }