bug: able to add negative modular credits to custom module

[tohhengxing]

Describe the bug

You can add negative MC when creating a custom module in module planner

To Reproduce

Steps to reproduce the behavior:

1. go to module planner
2. add a custom mod
3. click add data
4. input a negative number

Expected behavior

should not allow negative number to be added

Screenshots

https://user-images.githubusercontent.com/102740235/180600693-18652abe-4674-446a-a24a-6ab29eb05820.mp4