Cannot optimize a model twice

[guimarqu]

To Reproduce
Create a decomposed model

Then, call optimize! twice.

optimize!(model) # works
optimize!(model) # bug : MethodError: no method matching get_rowids_colids_vals(::Nothing)

Expected behavior
The second time I call optimize, optimization should restart from scratch.

Additional context
Tested in jupyter notebook

Tests
Should be tested in direct model & "normal mode".

• no reformulation + direct model
• no reformulation + no direct model
• reformulation + direct model
• reformulation + no direct model