Slow down a little and rereview the two errors, the one first reported and the one that occurred after resolving the first and before trying to provide the user_defined field.

The first error had to do with: products_discount_type, the second because of products_discount_type_from which is a different field. Originally both had '', then after resolving the first issue, only the second one had ''. Again will look at how both of those fields should behave, but this is/was the first report of that "issue".

As discussed elsewhere here, either those familiar with the plugin have self corrected it, had someone else do so without reporting the issue, have moved on to something else, or have operated in a way that didn't bring that to the surface. Regardless of their reasons, thank you for reporting this.