[Tests] GUI macOS test_discovered_page random fails

[drew2a]

The random test fails during #6629
console

=================================== FAILURES ===================================
_____________________________ test_discovered_page _____________________________

window = <tribler_gui.tribler_window.TriblerWindow object at 0x1321838b0>

    @pytest.mark.guitest
    def test_discovered_page(window):
        QTest.mouseClick(window.left_menu_button_discovered, Qt.LeftButton)
>       tst_channels_widget(window, window.discovered_page, "discovered_page", sort_column=2)

src/tribler-gui/tribler_gui/tests/test_gui.py:244: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

window = <tribler_gui.tribler_window.TriblerWindow object at 0x1321838b0>
widget = <tribler_gui.widgets.channelcontentswidget.ChannelContentsWidget object at 0x13380ac10>
widget_name = 'discovered_page', sort_column = 2, test_filter = True
test_subscribe = True

    def tst_channels_widget(window, widget, widget_name, sort_column=1, test_filter=True, test_subscribe=True):
        wait_for_list_populated(widget.content_table)
        screenshot(window, name=f"{widget_name}-page")
    
        # Sort
        widget.content_table.sortByColumn(sort_column, 1)
        wait_for_list_populated(widget.content_table)
        screenshot(window, name=f"{widget_name}-sorted")
        max_items = min(widget.content_table.model().channel_info["total"], 50)
        assert widget.content_table.verticalHeader().count() <= max_items
    
        # Filter
        if test_filter:
            old_num_items = widget.content_table.verticalHeader().count()
            QTest.keyClick(widget.channel_torrents_filter_input, 'r')
            wait_for_list_populated(widget.content_table)
            screenshot(window, name=f"{widget_name}-filtered")
            assert widget.content_table.verticalHeader().count() <= old_num_items
            QTest.keyPress(widget.channel_torrents_filter_input, Qt.Key_Backspace)
            wait_for_list_populated(widget.content_table)
    
        if test_subscribe:
            # Unsubscribe and subscribe again
            index = get_index_of_row_column(widget.content_table, 0, widget.model.column_position[Column.VOTES])
            widget.content_table.on_subscribe_control_clicked(index)
            QTest.qWait(200)
>           window.dialog.button_clicked.emit(0)
E           AttributeError: 'NoneType' object has no attribute 'button_clicked'

src/tribler-gui/tribler_gui/tests/test_gui.py:222: AttributeError

[devos50]

Hopefully, #6600 would fix this since it removes some of the qWait calls (I'll finish that PR ASAP).

[devos50]

I noticed an error in the test. When testing for subscribe, it always clicks the subscribe toggle in the first row. If this is a personal channel, however, this will fail since the row then does not have a subscribe toggle. This is probably the reason for the error reported in this issue. The easiest fix is probably to sort on the 'subscribed' column which ensures that the first row contains a non-personal channel that the user has not subscribed to. Evidence: