descriptors: fix analysis of missing signatures post #575 #1072

Job	Run time
linter	58s
linter_gui	3m 43s
unit_tests (1.54, ubuntu-latest)	3m 0s
unit_tests (1.54, macOS-latest)	3m 12s
unit_tests (1.54, windows-latest)	3m 6s
unit_tests (nightly, ubuntu-latest)	1m 16s
unit_tests (nightly, macOS-latest)	1m 53s
unit_tests (nightly, windows-latest)	2m 1s
unit_tests_gui (1.65, ubuntu-latest)	5m 45s
unit_tests_gui (1.65, macOS-latest)	6m 8s
unit_tests_gui (1.65, windows-latest)	9m 59s
unit_tests_gui (nightly, ubuntu-latest)	4m 46s
unit_tests_gui (nightly, macOS-latest)	5m 4s
unit_tests_gui (nightly, windows-latest)	5m 38s
	56m 29s

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