Avoid empty variables being marked as geometry fields (objects API registration) #15071

Job	Run time
End-to-end tests, chromium	15m 9s
Run the Django test suite	8m 34s
Run the Django test suite in reverse	6m 0s
End-to-end tests, firefox	19m 26s
Set up docker build 'dynamic' env variables	1s
End-to-end tests, webkit	13m 39s
Build and check documentation	3m 27s
docker_build (extensions, token_exchange,prefill_haalcentraalhr, all-extensions-) / Build image	2m 43s
docker_build (production) / Build image	2m 50s
Scan docker image	2m 24s
Simulate upgrading instances (2.8.2)	1m 24s
Check for unexepected OAS changes	5s
Generate SDKs from OAS	34s
Validate OAS	13s
Generate Postman collection from OAS	9s
Push Docker image	0s
update-docker-readme	0s
	1h 16m 38s

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