Joined challenges created with incorrect progress.

[VictorAZ12]

For each Active challenge a user creates, the progress should always start from 0. However, if a user creates a private habit first, then checks in to make some progress, and deletes that habit, every active challenges joined by this user will start from the progress of the deleted habit. Reproduction:

1. Create a habit, then checkin
2. Delete the habit using the "edit" button
3. Create a challenge
4. Join the challenge, the progress doesn't start from 0

[VictorAZ12]

Potential reason: new habits will probably use the id previously occupied by some other deleted habits, which caused incorrect habit progress mapping. Need to clear the progress as well when deleting a habit.