Reduce number of ways saying "line x/value x is not available in descriptor y" in our database

Right now, there are multiple ways missing data is represented in our DB, e.g.:

-1
null
1969-12-31 23:59:59.999000
""
{}
-1.0
[]
0

That's at least 8 ways how missing data can show up. Ideally, we would only have one, e.g. null, so we easily know that all non-null values are actual values and it might save space in the DB as well in the case of that weird epoch conversion.