fdo#40067: Fix for importing white space in strings (XLSX).

Change-Id: I2590bd8b0d0c1d853caead60cf3af1b865d7fed7
Reviewed-on: https://gerrit.libreoffice.org/9805
Reviewed-by: Muthu Subramanian K <muthusuba@gmail.com>
Tested-by: Muthu Subramanian K <muthusuba@gmail.com>