I have a program that generates this XSLT code:

<xsl:template match="/">
         <xsl:variable name="test" select="'    '" as="xs:string"/>
         <xsl:value-of select="
             if (normalize-space($test) eq '') then ()
             else xs:integer($test) div 10"/>
</xsl:template>

When I execute that XSLT code, I get this warning message:

Warning: SXWN9000 Evaluation will always throw a dynamic error: Cannot

Why am I getting that Warning message?

If you run with -explain then you will see that the variable is inlined
and the expression rewritten.
But I have never really learned to understand the output of -explain
fully so I guess you will have to wait until Michael Kay shows up to
tell you why Saxon gives the warning.