optimize Gif frames

lazpaint/image/uimage.pas

@@ -677,6 +677,7 @@ begin
       gif.ReplaceFullFrame(newFrameIndex, RenderedImage, gif.FrameDelayMs[newFrameIndex]);
     end;
 
+    gif.OptimizeFrames;
     s := FileManager.CreateFileStream(AOutputFilename,fmCreate);
     try
       gif.SaveToStream(s);