id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,pull_request,body,repo,type,active_lock_reason,performed_via_github_app,reactions,draft,state_reason
1181236173,I_kwDOCGYnMM5GaDvN,422,Reconsider not running convert functions against null values,9599,open,0,,,1,2022-03-25T20:22:40Z,2022-03-25T20:23:21Z,,OWNER,,"I just got caught out by the fact that `None` values are not processed by the `.convert()` mechanism https://github.com/simonw/sqlite-utils/blob/0b7b80bd40fe86e4d66a04c9f607d94991c45c0b/sqlite_utils/db.py#L2504-L2510

I had run this code while working on #420 and I wasn't sure why it didn't work:

```
$ sqlite-utils add-column content.db articles score float
$ sqlite-utils convert content.db articles score '
import random
random.seed(10)

def convert(value):
    global random
    return random.random()
'
```
The reason it didn't work is that the newly added `score` column was full of `null` values.

I fixed it by doing this instead:

    $ sqlite-utils add-column content.db articles score float --not-null-default 1.0

But this indicates to me that the design of `convert()` here may be incorrect.",140912432,issue,,,"{""url"": ""https://api.github.com/repos/simonw/sqlite-utils/issues/422/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,