[3.4] Hyphens in slugs throw exceptions

[bobdenotter]

If you have a contenttype like this:

dummies:
    slug: dummies-foo
    name: Dummies
    singular_slug: dummy-foo
    singular_name: Dummy
    fields:
        title:
            type: text
            class: large
            group: content
        slug:
            type: slug
            uses: title
        teaser:
            type: html
            height: 150px

It throws an exception:

Curiously enough, this does work:

dummies:
    slug: dummiesfoo
    name: Dummies
    singular_slug: dummyfoo
    singular_name: Dummy
    fields:
        title:
            type: text
            class: large
            group: content
        slug:
            type: slug
            uses: title
        teaser:
            type: html
            height: 150px

[bobdenotter]

pinging @rossriley

[bobdenotter]

Fixed in #7140