Another solution is to rethink your categories so that users don't find an empty category.
另一种解决方案是重新考虑划分类别，以便用户不会看到空类别。
The theory of Empty Category is one of the most important parts in Government-and Binding Theory.
空语类理论在管辖与约束理论中占有十分重要的位置。
Many categories do not contain multiple instances, so you can leave this property empty to indicate that no instance is associated with the category.
许多类别不包含多个实例，因此，您可以保持此属性为空，指示没有实例与此类别关联。
Many categories do not contain multiple instances, so you can leave this property empty to indicate that no instance is associated with the category.
许多类别不包含多个实例，因此，您可以保持此属性为空，指示没有实例与此类别关联。
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