WebHost: Fix NamedRange dropdown being blank instead of Custom for presets #20458

Job	Run time
Test hosting with 3.12 on ubuntu-latest	3m 8s
Test Python 3.8 ubuntu-latest	4m 46s
Test Python 3.9 ubuntu-latest	4m 10s
Test Python 3.10 ubuntu-latest	4m 12s
Test Python 3.11 ubuntu-latest	4m 11s
Test Python 3.12 ubuntu-latest	5m 46s
Test Python 3.8 windows-latest	6m 4s
Test Python 3.12 windows-latest	7m 47s
Test Python 3.12 macos-latest	3m 8s
	43m 12s

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