Fix: Unaffilated list for club ambassadors not assigned to a club

It's possible for a club ambassador to not be assigned to a club. If this happens they are still able to access the Club Admin Activity. The unaffiliated datagrid will error out if they're not assigned to a club (or chapter).

```
NoMethodError: undefined method `country_code' for #<NullChapterable:0x00007fd115046990>
```

This update will address this issue.

Refs: #5371

app/null_objects/null_chapterable.rb

@@ -18,4 +18,12 @@ def chapter_program_information
   def build_chapter_program_information
     ChapterProgramInformation.none
   end
+
+  def country
+    nil
+  end
+
+  def country_code
+    nil
+  end
 end