```
ERROR: LoadError: LoadError: ArgumentError: collection must be non-empty
Stacktrace:
[1] _extrema_itr(f::typeof(identity), itr::Vector{Float64})
@ Base ./operators.jl:483
[2] _extrema_dims
@ ./multidimensional.jl:1698 [inlined]
[3] #extrema#486
@ ./multidimensional.jl:1685 [inlined]
[4] extrema
@ ./multidimensional.jl:1685 [inlined]
[5] concrete_term
@ ~/.julia/packages/StatsModels/lqOhh/src/schema.jl:201 [inlined]
[6] concrete_term(t::StatsModels.Term, xs::Vector{Float64}, #unused#::Nothing)
@ StatsModels ~/.julia/packages/StatsModels/lqOhh/src/schema.jl:198
[7] concrete_term(t::StatsModels.Term, dt::NamedTuple{(
@ StatsModels ~/.julia/packages/StatsModels/lqOhh/src/schema.jl:184
[8] (::StatsModels.var"#52#53"{NamedTuple{(
@ StatsModels ./none:0
[9] iterate
@ ./generator.jl:47 [inlined]
[10] Dict{StatsModels.Term, StatsModels.AbstractTerm}(kv::Base.Generator{Vector{StatsModels.Term}, StatsModels.var"#52#53"{NamedTuple{(
@ Base ./dict.jl:103
[11] Schema
@ ~/.julia/packages/StatsModels/lqOhh/src/schema.jl:37 [inlined]
[12] schema
@ ~/.julia/packages/StatsModels/lqOhh/src/schema.jl:123 [inlined]
[13] schema(f::StatsModels.FormulaTerm{StatsModels.Term, Tuple{StatsModels.FunctionTerm{typeof(|), var"#39#42",
@ StatsModels ~/.julia/packages/StatsModels/lqOhh/src/schema.jl:126
[14] LinearMixedModel(f::StatsModels.FormulaTerm{StatsModels.Term, Tuple{StatsModels.FunctionTerm{typeof(|),
@ MixedModels ~/.julia/packages/MixedModels/DCOiy/src/linearmixedmodel.jl:57
[15] fit(::Type{LinearMixedModel}, f::Stats
```

I’m not sure if this is a MixedModels.jl question (@dmbates) or a StatsModels.jl question (@dave.f.kleinschmidt )but I’m wondering what the error means and/or how to fix it.