XSLT assign a space as value

I am looking for replace null values with space if any in given loop .

<xsl:for-each select="msxsl:node-set($rowData)/cell">
   <td align="center" uniqueID="ms__id{$startingId + position() - 1}">
      <xsl:value-of select="@value">
      </xsl:value-of>
   </td>
</xsl:for-each>

Loop is within template Here @value is fetching value from a varicable

If @value do not holds any data alignment of table is being disturbed so I thought replacing null with   can help me.

Sagar Makhesana