Fix `DownloadState.get_ratio()` #3064

Job	Run time
gatekeeper	13s
env	1s
changes	5s
mac	0s
windows	0s
documentation	0s
ubuntu	0s
guitest	0s
pytest	0s
application_tester	0s
application_tester_draft / run (ubuntu-latest)	4m 11s
coverage_draft / generate and upload	3m 19s
guitest_draft / run (windows-latest)	3m 17s
scripttest_draft / run	1m 53s
	12m 59s

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