UI: Disable Copy Filters in scene list for scene with no filters

When you right-click on a source in the Sources list that does not have
any filters, the "Copy Filters" item is disabled. When you right-click
on a scene in the Scenes list that does not have any filters, the "Copy
Filters" item is enabled. This fixes the Scenes context menu to behave
like the Sources context menu.
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Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f