Fix AssetBrowser UI errors

Steps to reproduce:
- enable Extended Asset Browser
- open a regular File Browser

gives:
"rna_uiItemR: property not found: FileSelectParams.asset_category"

Now do proper poll.

Differential Revision: https://developer.blender.org/D12350

release/scripts/startup/bl_ui/space_filebrowser.py

@@ -655,7 +655,10 @@ class ASSETBROWSER_PT_navigation_bar(asset_utils.AssetBrowserPanel, Panel):
 
     @classmethod
     def poll(cls, context):
-        return context.preferences.experimental.use_extended_asset_browser
+        return (
+            asset_utils.AssetBrowserPanel.poll(context) and
+            context.preferences.experimental.use_extended_asset_browser
+        )
 
     def draw(self, context):
         layout = self.layout