Fix Palette bugs reported by patyhank

level/bitstorage.go

@@ -182,3 +182,15 @@ func (b *BitStorage) WriteTo(w io.Writer) (int64, error) {
 	}
 	return n, nil
 }
+
+func (b *BitStorage) Fix(bits int) error {
+	b.mask = 1<<bits - 1
+	b.bits = bits
+	b.valuesPerLong = 64 / bits
+	// check data length
+	dataLen := calcBitStorageSize(bits, b.length)
+	if l := len(b.data); l != dataLen {
+		return newBitStorageErr{ArrlLen: l, WantLen: dataLen}
+	}
+	return nil
+}

level/palette.go

@@ -150,7 +150,7 @@ func (p *PaletteContainer[T]) ReadFrom(r io.Reader) (n int64, err error) {
 	if err != nil {
 		return n, err
 	}
-	return n, nil
+	return n, p.data.Fix(int(nBits))
 }
 
 func (p *PaletteContainer[T]) WriteTo(w io.Writer) (n int64, err error) {