Fixed _requestedCommits enumeration

src/Avalonia.Base/Media/MediaContext.Compositor.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Linq;
 using System.Threading.Tasks;
 using Avalonia.Platform;
 using Avalonia.Rendering.Composition;
@@ -78,7 +79,7 @@ partial class MediaContext
             // Nothing to do, and there are no pending commits
             return false;
         
-        foreach (var c in _requestedCommits)
+        foreach (var c in _requestedCommits.ToArray())
             CommitCompositor(c);
         
         _requestedCommits.Clear();