Describe the bug
A clear and concise description of what the bug is.
Whenever a user downvotes a tutorial the down vote count goes to negative and does not stop at zero.
To Reproduce
Steps to reproduce the behavior:

1. Click on the profile icon on the top right corner and select "My Profile" from the drop down
2. Go to any of the tutorials and downvote the tutorials
3. you will be able to see the down votes going in negative

Expected behavior
A clear and concise description of what you expected to happen.
The downvote count should not go below zero

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: MacOS
• Browser Safari
• Version v4.5.2