Changes
Make it work with an empty parameter (fall back on current page)
{{#if: {{#titleparts:{{#if:{{{1|}}}|{{{1}}}|{{FULLPAGENAME}}}}}|-1}} | {{#titleparts:{{#if:{{{1|}}}|{{{1}}}|{{FULLPAGENAME}}}}|-1}}|-{{#if:{{{1|}}} | {{{1}}}|{{FULLPAGENAME}}}}} }}<noinclude>
{{documentation}}
</noinclude>