Support a no-op for headline pre-blank.

src/wasm/plain_list_item.rs

@@ -8,6 +8,7 @@ use crate::compare::ElispFact;
 use crate::types::CheckboxType;
 use crate::types::PlainListItem;
 use crate::types::PlainListItemCounter;
+use crate::types::PlainListItemPreBlank;
 use crate::wasm::to_wasm::ToWasmStandardProperties;
 
 #[derive(Debug, Serialize, Deserialize)]
@@ -17,7 +18,7 @@ pub struct WasmPlainListItem {
     pub(crate) counter: Option<PlainListItemCounter>,
     pub(crate) checkbox: Option<String>,
     #[serde(rename = "pre-blank")]
-    pub(crate) pre_blank: usize,
+    pub(crate) pre_blank: PlainListItemPreBlank,
 }
 
 to_wasm!(
@@ -52,7 +53,7 @@ to_wasm!(
                     }
                     .to_owned()
                 }),
-                pre_blank: 0, // TODO: Should this be a no-op?
+                pre_blank: original.pre_blank,
             },
         ))
     }