Inconsistent empty feature values when creating or editing

[rolodato]

How are you running Flagsmith

• [ ] Self Hosted with Docker
• [ ] Self Hosted with Kubernetes
• [X] SaaS at flagsmith.com
• [ ] Some other way (add details in description below)

Describe the bug

When a feature is created without a value, its value is set to null. However, if its value is set to non-empty and later set back to empty, the resulting value will be set to "". Setting the feature to have a value of null requires a manual API call.

Steps To Reproduce

1. Create a feature without a value
2. Click "Run test" in the Features list - that feature will have a value of null
3. Edit the feature to have some other value
4. Edit the feature again and delete its value
5. Click "Run test" again - the feature will now have a value of ""

Expected behavior

Erasing a feature's value should return it to the exact same state as when it was created without a value. Because we're not making the type choice explicit in the UI, IMO the correct solution would be to always save empty features as null.

Screenshots

No response