Allow switching tracks on the fly

pico.js

         State.online.forEach(signalPeerStop)
     },
     view() {
-        if(!State.media[State.username]) {
-            return m('.media',
-                m('.media-settings',
-                    m('button', {onclick: Media.turnOn}, 'turn on'),
-                    m('select#media-source', Media.videoSources.map(option => m('option', option))),
-                    m('label', m('input#mute-check', {type: 'checkbox'}), 'mute'),
-                ),
-            )
-        }
-        else {
-            return m('.media',
-                m('.media-settings',
-                    m('button', {onclick: Media.turnOff}, 'turn off'),
-                ),
-                m('.videos',
-                    Object.entries(State.media).map(([username, stream]) =>
-                        m(Video, {username, stream})
-                    ),
+        return m('.media',
+            m('.media-settings',
+                State.media[State.username]
+                ? m('button', {onclick: Media.turnOff}, 'turn off')
+                : m('button', {onclick: Media.turnOn}, 'turn on')
+                ,
+                m('select#media-source', Media.videoSources.map(option => m('option', option))),
+                m('label', m('input#mute-check', {type: 'checkbox'}), 'mute'),
+            ),
+            m('.videos',
+                Object.entries(State.media).map(([username, stream]) =>
+                    m(Video, {username, stream})
                 ),
-            )
-        }
-    }
+            ),
+        )
+    },
 }
 const Login = {
     sendLogin: (e) => {