Fix replacing of a video with a new one.

This was broken when we implemented local videos.

static/sfu.js

@@ -1050,7 +1050,6 @@ function setMedia(c, isUp, video) {
             media = document.createElement('video');
             if(isUp)
                 media.muted = true;
-            media.srcObject = c.stream;
         }
 
         media.classList.add('media');
@@ -1063,6 +1062,9 @@ function setMedia(c, isUp, video) {
             addCustomControls(media, div, c);
     }
 
+    if(!video)
+        media.srcObject = c.stream;
+
     let label = document.getElementById('label-' + c.id);
     if(!label) {
         label = document.createElement('div');