"role attribute has valid value" (674b10): make rule inapplicable if there isn't at least one role

[Jym77]

Make rule inapplicable on role=" " because whitespace only role attribute is treated as empty one (there is no token in the set of space separated tokens).

Closes issue(s):

• closes Failed example 3 wrong for 'role attribute has valid value' #1131

Need for Final Call:
This will require a 1 week Final Call (upgrade in applicability, changes one example)

---

Pull Request Etiquette

When creating PR:

• Make sure you're requesting to pull a branch (right side) to the develop branch (left side).

After creating PR:

• Add yourself (and co-authors) as "Assignees" for PR.
• Add label to indicate if it's a Rule, Definition or Chore.
• Close the issue that the PR resolves (and make sure the issue is referenced in the top of this comment)
• Optionally request feedback from anyone in particular by assigning them as "Reviewers".

How to Review And Approve

• Go to the “Files changed” tab
• Here you will have the option to leave comments on different lines.
• Once the review is completed, find the “Review changes” button in the top right, select “Approve” (if you are really confident in the rule) or "Request changes" and click “Submit review”.
• Make sure to also review the proposed Final Call period. In case of disagreement, the longer period wins.

Change accepted.

[Jym77]

Final Call ends on May 1st.

[Jym77]

Final Call has ended. Merging.