[xsl] Possible to pass 'empty sequence' to function?

Hi,
Using Saxon 8 and XSLT 2.0, I have some functions defined in my
stylesheet using <xsl:function/>.

These functions usually have parameters to pass it an element.  The
trasnformation fails when I pass an empty sequence as a parameter. 
Since I may call a particular function as part of my xpath from many
parts of the stylesheet, I would much rather the function handle null
elements rather than doing it at each place I call it.
Is there no way to allow my function to accept empty sequence parameters??

Thanks!