fix

examples/examples-browser/views/demo.html

@@ -306,10 +306,13 @@ var videoEl = inputVideo;
   };
     var f0 = async function() {
 
-
-        const stream = await navigator.mediaDevices.getUserMedia({ video: {} })
+      try{
+        const stream = await navigator.mediaDevices.getUserMedia( { video: {} } )
         const videoEl = inputVideo
         videoEl.srcObject = stream
+      }catch(e){
+        console.error('no media device')
+      }
         f()
     }
     f0();