fix: clear black bg after camera capture

package.json

@@ -1,6 +1,6 @@
 {
   "name": "qrcode-decoder",
-  "version": "0.1.0",
+  "version": "0.1.1",
   "description": "Tool for decoding qrcode",
   "main": "dist/index.js",
   "jsnext:main": "dist/index.esm.js",

src/index.js

@@ -306,6 +306,9 @@ class QrcodeDecoder {
             const track = this.stream.getTracks()[0];
             track.stop();
             this.stream = undefined;
+
+            // fix: clear black bg after camera capture
+            this.videoElem.srcObject = null;
         }
 
         if (this.timerCapture) {