[request] Improve null values error handling

[akamensky]

CH defaults to NOT NULL for columns, which is different from many other databases that default to NULL. Because of this it appears to be common that users will get NPE error which does not specify the cause of failure.

The error here is very generic and does not point in the right direction. The point of having error messages at all is to make it clear what happened and possibly point to correct solution.

I suggest to:

• catch this exception
• and check if the exception happened because of null being received for non-nullable column
• if it is then throw another exception which provides much clearer message (i.e. received NULL value for NOT NULL column or something similar, maybe even include column name in the message if possible).

This will allow users to handle those issues in much cleaner way.