Use {{IfNotTranslation|{{FULLPAGENAME}}|{{BASEPAGENAME}}}} instead of {{FULLPAGENAME}}.
Topic on Template talk:Extension
SOFIXIT?
Why not use always {{BASEPAGENAME}}? It should also work on english pages. You'll need also {{NAMESPACE}}.
Use {{IfNotTranslation|{{FULLPAGENAME}}|{{BASEPAGENAME}}}} instead of {{FULLPAGENAME}}.
SOFIXIT?
Why not use always {{BASEPAGENAME}}? It should also work on english pages. You'll need also {{NAMESPACE}}.