Impossible to import a model without a grid.

[albop]

Should be possible.

Fails with:

KeyError: key :tag not found

Stacktrace:
 [1] getindex(::Dict{Any,Any}, ::Symbol) at ./dict.jl:478
 [2] #get_grid#146(::Dict{Any,Any}, ::Function, ::Model{Symbol("##377")}) at /home/pablo/.julia/dev/Dolo/src/model.jl:174
 [3] get_grid at /home/pablo/.julia/dev/Dolo/src/model.jl:167 [inlined]
 [4] (::getfield(Dolo, Symbol("##call#149#160")))(::Bool, ::String, ::Type{Model{Symbol("##377")}}, ::Dict{Symbol,Any}) at /home/pablo/.julia/dev/Dolo/src/model.jl:238
 [5] (::getfield(Core, Symbol("#kw#Type")))(::NamedTuple{(:print_code, :filename),Tuple{Bool,String}}, ::Type{Model{Symbol("##377")}}, ::Dict{Symbol,Any}) at ./none:0
 [6] #Model#171(::Bool, ::Type, ::String) at /home/pablo/.julia/dev/Dolo/src/model.jl:308
 [7] Model(::String) at /home/pablo/.julia/dev/Dolo/src/model.jl:299
 [8] top-level scope at In[17]:1