Repair is type in list
Created by: clusterfack
Using isnum is unreliable for detecting nonstandard formats of already associative lists. Causing them to be overriden with the type cache.
Checking isnull instead will allow us to detect strings, numbers, lists, typepaths, basically everything that we want to check to make sure this isn't already an associative list.
Fixes #10225 (closed) Fixes #10224 (closed)