**Steps: **
1. Set https://es.wikipedia.beta.wmflabs.org/wiki/MediaWiki:GrowthExperimentsSuggestedEdits.json to `{}` (to reset the state of the form).
1. Go to https://es.wikipedia.beta.wmflabs.org/wiki/Especial:CommunityConfiguration/GrowthSuggestedEdits
Fields such as "The maximum number of "Add an image to an unillustrated article" suggested tasks a newcomer can complete daily" do not have any saved values.
2. Change a different field and save the form. The save will be successful.
3. Set "The maximum number of "Add an image to an unillustrated article" suggested tasks a newcomer can complete daily" to an arbitrary delete and save the form. The save will be successful.
3. Now, delete the previously entered number and hit **Save changes** - the error message will be displayed:
{F49881397}
Screencast that demonstrates this bug is at https://drive.google.com/file/d/1uYKoCddO2aWxTdxHYJOnJ69OkyQvJB2S/view?usp=sharing.
**Expected behavior**:
- null values should be allowed
- or numerical fields should have fall-back default values
- a user warning should provide a user with clearer info of what went wrong and how the failure can be corrected