Fix undefined subtitle for angular course in course card

[Svetzayats]

🐛 Describe the Bug

Undefined in subtitle for angular course

🔄 Steps to Reproduce

Go to Courses page

🏁 Actual Behavior

Undefined as a subtitle

🏁 Expected Behavior

Empty string if subtitle is not provided

📸 Screenshots

ℹ️ Additional Context

I have fix (and updated tests), need task number for creating a PR

[SpaNb4]

#1061