Ensure poster image is not downloaded again for HTML5 videos

src/js/ui.js

@@ -172,6 +172,11 @@ const ui = {
         // Set property synchronously to respect the call order
         this.media.setAttribute('poster', poster);
 
+        // HTML5 uses native poster attribute
+        if (this.isHTML5) {
+            return Promise.resolve(poster);
+        }
+
         // Wait until ui is ready
         return (
             ready