Fix handling of model-local variable in _params_derivs
The attached mod-files has a model-local variable
#SAVBAR = steady_state(iv)/( steady_state(y)
that causes a crash in master
with
Undefined function or variable 'SAVBAR__'.
Error in Kim2003.static_params_derivs (line 35) T(1) = 1-SAVBAR__;
Error in getH (line 158)
which shows that the substitution in the file is broken. It still worked in 4.5
Kim2003.mod