On Behalf profile does not select org profile by default if contribution profiles are added prior to it

If the pre & post profiles are selected before the on behalf of profiles are selected, enabling and disabling the is_onbehalf checkbox on the settings page does not retrieve the org selected.
To replicate:

1. Create a contribution page without selecting "Allow individuals to contribute and / or signup for membership on behalf of an organization?"
2. Add one or two profiles under the profiles tab.
3. Navigate back to the Title tab and enable "Allow individuals to contribute and / or signup for membership on behalf of an organization?"
4. Save the contribution page.
5. Now disable the checkbox "Allow individuals to contribute and / or signup for membership on behalf of an organization?"
6. Save the contribution page.
7. Enable the checkbox "Allow individuals to contribute and / or signup for membership on behalf of an organization?" once more. You will see that the default organization is not selected.
This is because the code creates an entry for uf_group_id = one of the pre/post profiles selected for the module on_behalf.

I will be sending a PR with the patch and the appropriate webtest.