Nested custom properties with preserve false does not work correctly #233

▼ before
:root {
  --my-blue: blue;
}

// "--my-red" does not exist
.sample {
  color: var(--my-red, var(--my-blue))
}

▼ after
.sample {
  color: var(--my-blue) <-- can't resolve the custom properties
}

▼ before
:root {
  --my-blue: blue;
}

// "--my-red" does not exist
.sample {
  color: var(--my-red, var(--my-blue))
}

▼ after
:root {
  --my-blue: blue;
}
.sample {
  color: var(--my-blue) <-- it can resolve the custom properties
}