Use then/catch

pico.js

     },
     getSelectedMedia: async () => {
         const stream = new MediaStream()
+        const addTrack = stream.addTrack.bind(stream)
 
         const muted = document.querySelector('#mute-check').checked
         if(!muted) {
             const audio = Media.audioDefaults
-            const audioStream = await navigator.mediaDevices.getUserMedia({audio})
-            audioStream.getAudioTracks().forEach(track => stream.addTrack(track))
+            await navigator.mediaDevices.getUserMedia({audio})
+                .then(s => s.getAudioTracks().forEach(addTrack))
+                .catch(e => console.error(e))
         }
 
         const source = document.querySelector('#media-source').value
         if(source === 'camera') {
             const video = {width: {ideal: 320}, facingMode: 'user', frameRate: 26}
-            const videoStream = await navigator.mediaDevices.getUserMedia({video})
-            videoStream.getVideoTracks().forEach(track => stream.addTrack(track))
+            await navigator.mediaDevices.getUserMedia({video})
+                .then(s => s.getVideoTracks().forEach(addTrack))
+                .catch(e => console.error(e))
         }
         if(source === 'screen' && navigator.mediaDevices.getDisplayMedia) {
-            const videoStream = await navigator.mediaDevices.getDisplayMedia()
-            videoStream.getVideoTracks().forEach(track => stream.addTrack(track))
+            await navigator.mediaDevices.getDisplayMedia()
+                .then(s => s.getVideoTracks().forEach(addTrack))
+                .catch(e => console.error(e))
         }
 
         return stream