Fix ordinary semantic parser initializer under test configuration

crates/oa-core/src/language/semantic_source.rs

@@ -194,6 +194,8 @@ pub(super) fn row_key(source: &str, origins: &BTreeMap<Id, Id>) -> Option<String
         cursor: 0,
         value_depth: 0,
         limits: ParseLimits::UNLIMITED,
+        #[cfg(test)]
+        mixed: None,
     };
     let ast = parser.value().ok()?;
     let facet = serde_json::from_value(raw(&ast).ok()?).ok()?;