Kusto Query Assistance - Azure Sign In Logs

Question

I'm new to this language and seems pretty straight forward however, I'm unsure how to drill down into tables to filter.

I'm trying to write a query that will show me all sign in's that aren't from within Australia

SigninLogs
| where LocationDetails !contains "AU"

This is fine, however, it sometimes returns blank results as it will show an MFA entry where the location is blank:

This is what a valid result with a location looks like in the logs:

Ultimately, what I'm trying to do is:

Get me all sign in's that are Outside of Australia and DO NOT return anything where the geocoordinates are blank

This is the closest query I've come to but it's still not achieving the above:

SigninLogs
| where LocationDetails !contains "AU"
| where LocationDetails != isnull("geoCoordinates")

Any help would be appreciated! Thanks.