The leveled list patcher has a feature that removes empty sublists from leveled lists.
This is intended to help with mods that accidentally added empty leveled lists to another leveled list, which can cause the leveled list to select nothing.

However, as Elminster pointed out on Discord, this can actually break mods. The problem is that some mods create empty leveled lists and fill them via scripts at runtime, and the patcher obviously can't distinguish between these two use cases.
For Skyrim and newer games, Papyrus exposes this functionality directly, while older games can do it via xSE (the AddToLeveledList function).
Note: We're pretty much all in agreement that this is an absolutely awful idea that makes patching the mod in question a nightmare, but it's an established practice used by several very popular mods such as Immersive Armors.

Other options would be to enable the option by default or to remove the feature entirely.