fix/bug: internet check runs after sidebar opens instead of before

[Bindkushal]

Bug

In _on_chat_button_clicked (AbiWordActivity.py ~L266), the internet
check runs after the sidebar is already open:

else:
    self.chat_sidebar.toggle_visibility()   # opens first
    if not self.check_internet_connection():
        self._show_no_internet_dialog()     # then checks

What happens

1. User clicks Chat with no internet
2. Sidebar opens
3. "No Internet" dialog appears
4. User closes dialog — sidebar stays open with no way to use it

Expected behaviour

Check internet first. If offline, show the dialog and do not open the sidebar.