Hey @DiegoMorales - welcome to the community! 
This is definitely something that has come up before, as you can see here. The solution is relatively straightforward for simple queries but will be kind of a pain for bulk inserts.
Essentially, you'll need to iterate through query1.data and replace any null values with { RT$BQ: 'DATATYPE', value: null }. I'd probably recommend defining a transformer on query1 that does this. It might look something like:
Let me know if you have any questions about implementing this!