fix the continue block parse error

worksheet.go

@@ -92,7 +92,7 @@ func (w *WorkSheet) parseBof(buf io.ReadSeeker, b *bof, pre *bof) *bof {
 		binary.Read(buf, binary.LittleEndian, &c.BlankCol)
 		var count uint16
 		binary.Read(buf, binary.LittleEndian, &count)
-		c.Str = w.wb.get_string(buf, count)
+		c.Str, _ = w.wb.get_string(buf, count)
 		col = c
 	case 0x201: //BLANK
 		col = new(BlankCol)