fix(core): catch missing reduced costs and shadow prices. (#1383)

* fix(core): catch missing reduced costs and shadow prices. Fixes #1381 and #1372

* Added fix to next release

Author: Palaract

release-notes/next-release.md

@@ -5,6 +5,7 @@
 ## Fixes
 
 * Fixes the incorrect bounds in the CycleFree loop removal.
+* Fixes reduced costs and shadow prices not available when using non-convex models.
 
 ## Other
 

src/cobra/core/solution.py

@@ -174,7 +174,15 @@ def get_solution(
     reduced = np.empty(len(reactions))
     var_primals = model.solver.primal_values
     shadow = np.empty(len(metabolites))
-    if model.solver.is_integer:
+
+    try:
+        var_duals = model.solver.reduced_costs
+        constr_duals = model.solver.shadow_prices
+        duals_available = True
+    except Exception:
+        duals_available = False
+
+    if model.solver.is_integer or not duals_available:
         reduced.fill(np.nan)
         shadow.fill(np.nan)
         for i, rxn in enumerate(reactions):