I am doing some testing on a custom collation sequence, and I find that no NULL values are passed to the collation sequence as arguments. After a little looking I found this [post](http://sqlite.1065341.n5.nabble.com/Collation-blobs-tp38508p38509.html) on the old Nabble archive. My testing confirms that no NULL values are passed to my custom collation sequence. Can I positively assert that no NULL values will _ever_ be passed to the collation sequence?