Fix: Don't use self._set_column when adding variables.

This lead to index error in example cuttingstock_cg.py, because _set_column uses
the mip.Var object which is not yet added to the mip.Model.

Instead, manually set the coefficients.

Author: rschwarz

mip/highs.py

@@ -299,7 +299,11 @@ def add_var(
             )
 
         if column:
-            self._set_column(col, column)
+            # Can't use _set_column here, because the variable is not added to
+            # the mip.Model yet.
+            # self._set_column(col, column)
+            for cons, coef in zip(column.constrs, column.coeffs):
+                self._change_coef(cons.idx, col, coef)
 
         # store name & type
         self._var_name.append(name)