[syslinux] Fixed the case where ITARGET is empty

x86/syslinux/syslinux.conf

@@ -20,9 +20,9 @@ var_append makeopt ' ' '$ITARGET'
 
 hook_add preconf 5 'syslinux_itarget_prepare'
 syslinux_itarget_prepare() {
-	export ITARGET=$( grep ^ITARGET Makefile | cut -d= -f2- )
+	export ITARGET=$( grep ^ITARGET Makefile | cut -d= -f2- | sed -e 's/^ *//' )
 	
-	rm -v $ITARGET
+	[ -z "$ITARGET" ] || rm -v $ITARGET
 }
 
 # install mkdiskimage