Simple Food Menus - Multiple new sections generates errors in section page output

#### Steps to reproduce the issue

1. Go to Food Menus > Menu Items and add a new Menu Item.
2. In the Menu Sections box, add at least two new Menu Sections.
3. Publish the Menu Item.
4. Publish another Menu item with only one Menu Section assigned.
5. View both Menu Section pages.

#### What I expected

I expected to only be able to assign one Menu Section to each Menu Item, which happens when the Menu Sections already exist.

I expected each Menu Section page to show the correct title, description and menu items, even if Menu Items are assigned to multiple Menu Sections (since I was able to assign Multiple Sections to a Menu Item as described above).

#### What happened instead

When adding new Menu Sections, it allows me to add multiple Menu Sections to one Menu Item.

Screencast: https://cloudup.com/cdLIVLaiA1Q

The Menu Section page shows the title, description and Menu Items from both Menu Sections (because of the Menu Items assigned to multiple Menu Sections).

Reproduce the issue through Food Menus > Menu Items by creating multiple new Menu Sections, publishing the items, and opening both Menu Section pages. Trace the Menu Section page output and confirm that each page shows only its own title, description, and menu items, while clarifying whether multiple section assignments should be allowed.

Written by the indexing model from the issue text.