Fix T90341: Crash opening 2.4 file with File Browser editor open

The file selection parameters (e.g. `context.space_data.params`) are
expected to be unset in certain cases. Reading 2.4 files seems to be one
of them. Hence, code using it should check it's set first. Also added an
assert to a File Browser UI template printing a message when the
parameters are unset, to help debugging the issue.

release/scripts/startup/bl_ui/space_filebrowser.py

@@ -373,6 +373,7 @@ class FILEBROWSER_PT_advanced_filter(Panel):
     def poll(cls, context):
         # only useful in append/link (library) context currently...
         return (
+            context.space_data.params and
             context.space_data.params.use_library_browsing and
             panel_poll_is_upper_region(context.region) and
             not panel_poll_is_asset_browsing(context)
@@ -423,6 +424,10 @@ class FILEBROWSER_PT_directory_path(Panel):
 
         return True
 
+    @classmethod
+    def poll(cls, context):
+        return context.space_data.params
+
     def draw(self, context):
         layout = self.layout
         space = context.space_data