Fix advanced links (#101)

* Save the data of the advanced links in the content

* Avoid console error if the header has no first child

* Remove totally useless statement

Author: brichet

gluepyter/glue_ydoc.py

@@ -251,7 +251,6 @@ def add_links_to_contents(self, links: Dict[str, Dict], contents: Dict):
                     list_name = f"list{'' if lists_count < 0 else f'_{lists_count}'}"
                     lists_count += 1
                     link.pop(f"cids{i}_labels", None)
-                    link.pop(f"data{i}", None)
                     attr_list = {
                         "_type": "builtins.list",
                         "contents": link.pop(f"cids{i}", []),

src/linkPanel/linkEditor.ts

@@ -60,7 +60,7 @@ export class LinkEditor extends BoxPanel {
     );
     maxHeight = Math.max(
       ...headers.map(
-        header => (header?.node.firstChild as HTMLElement).offsetHeight || 0
+        header => (header?.node.firstChild as HTMLElement)?.offsetHeight || 0
       )
     );
     headers.forEach(header => {