I resolved this by putting if/else statements with the variables that were missing and setting the values to 0 or null if the key-value pair was missing.

This is the URL I used to return Stack Overflow's top twenty users sorted by reputation and listing only their name, age and location:

https://api.stackexchange.com/2.2/users?pagesize=20&order=desc&sort=reputation&site=stackoverflow&filter=!T6ovp2_VscH*jnbDel