The issue I raised initially (before Jarno pointed out that your
stylesheet should not run at all). Unless you have specified
xsl:strip-space you are sorting on the amount of indentation space used
in your elements.

Also you probably want to use
<xsl:apply-templates select="object">
rather than <xsl:apply-templates>

as otherwise (again unless you are using strip-space) you will select
all the inter-element space (and sort all this space together at the
start of the list)