Fix building of reference border in the bottom of the frame.
Fix building of reference border in the bottom of the frame.

- Don't write to the top-left corner during construction of left border,
  because that is handled later that is handled later.

ultravideo/kvazaar,ultravideo/kvazaar,ultravideo/kvazaar,lu-zero/kvazaar,ultravideo/kvazaar,lu-zero/kvazaar,lu-zero/kvazaar,ultravideo/kvazaar,lu-zero/kvazaar