Don't call bar.SetRefill with negative numbers

If srcInfo.Size == -1, the progress bar is not showing the
refill value anyway (customPartialBlobDecorFunc is only
used if size is known), so don't bother calling this function
with nonsense data, if anything, at least to emphasize that this
condition is, in principle, possible.

Should not affect behavior, hopefully.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

copy/copy.go

@@ -1210,7 +1210,9 @@ func (ic *imageCopier) copyLayer(ctx context.Context, srcInfo types.BlobInfo, to
 			}
 			info, err := ic.c.dest.PutBlobPartial(ctx, &proxy, srcInfo, ic.c.blobInfoCache)
 			if err == nil {
-				bar.SetRefill(srcInfo.Size - bar.Current())
+				if srcInfo.Size != -1 {
+					bar.SetRefill(srcInfo.Size - bar.Current())
+				}
 				bar.mark100PercentComplete()
 				hideProgressBar = false
 				logrus.Debugf("Retrieved partial blob %v", srcInfo.Digest)