Feat: empty messages when user hasn't solved any exams

[ricardo177m]

When a user hasn't solved any exam, a message is shown on its profile.

Notion tasks:

• https://www.notion.so/67c560114b234cf38a5ee26dd22362cc?v=91204d54737041399cba233e30b5c015&p=c9949e9f44104716aa49a49c9860df5d&pm=s
• https://www.notion.so/67c560114b234cf38a5ee26dd22362cc?v=91204d54737041399cba233e30b5c015&p=d53ae032eb694660803fa0764d4fe50d&pm=s

These two tasks can be merged.

Demo