Unclear circular learning path

[dwalizer]

A situation can arise where a circular learning path can occur but the message warning the user of it is unclear.

Steps:

• Create a new project
• Create two subjects
• In Subject 1, create 5 skills (Skill 1 through Skill 5)
• In Subject 2, create skills 6 through 10
• In the learning path, add Skill 6 as a prerequisite for both Skill 5 and Skill 7
• Add Skill 5 as a prerequisite for Skill 9
• Add Skill 7 as a prerequisite for Skill 8
• Create two badges
• In Badge 1, add Skill 1 and Skill 5
• In Badge 2, add Skill 6 through 10
• In the learning path, attempt to add Skill 9 as a prerequisite of Skill 10

You should get an error about the circular learning path, indicating that Skill 10 is already in the learning path, even though it is not visibly present. Additionally, attempting to copy the project will fail, as it will turn out that a circular learning path already exists. This should've been prevented from happening both on the Learning Path page and the Badge page.