"Variants and multipart cannot be both empty!"

[Nobookie]

Trying to convert a resource pack called Stay True.

stay_true.zip

Exception in thread "main" java.lang.IllegalArgumentException: variants and multipart cannot be both empty!
        at team.unnamed.creative.blockstate.BlockStateImpl.validate(BlockStateImpl.java:57)
        at team.unnamed.creative.blockstate.BlockStateImpl.<init>(BlockStateImpl.java:52)
        at team.unnamed.creative.blockstate.BlockState.of(BlockState.java:87)
        at team.unnamed.creative.serialize.minecraft.blockstate.BlockStateSerializer.deserializeFromJson(BlockStateSerializer.java:117)
        at team.unnamed.creative.serialize.minecraft.blockstate.BlockStateSerializer.deserializeFromJson(BlockStateSerializer.java:49)
        at team.unnamed.creative.serialize.minecraft.MinecraftResourcePackReaderImpl.read(MinecraftResourcePackReaderImpl.java:265)
        at team.unnamed.creative.serialize.minecraft.MinecraftResourcePackReader.readFromZipFile(MinecraftResourcePackReader.java:93)
        at team.unnamed.creative.serialize.minecraft.MinecraftResourcePackReader.readFromZipFile(MinecraftResourcePackReader.java:81)
        at org.geysermc.pack.converter.PackConverter.lambda$convert$2(PackConverter.java:258)
        at org.geysermc.pack.converter.util.ZipUtils.openFileSystem(ZipUtils.java:125)
        at org.geysermc.pack.converter.PackConverter.convert(PackConverter.java:251)
        at org.geysermc.pack.converter.bootstrap.Main.main(Main.java:60)