Fix corner case of cpsat encoding :

- when no task is consuming in resource, we don't include constraints storing the consumption of this resource, because it leads to failed model. (addMaxEquality most probably or NonOverlap are not compliant with empty list of variables)

discrete_optimization/rcpsp/solver/cpsat_solver.py

@@ -346,6 +346,9 @@ def create_cumulative_constraint_and_used_resource(
                 for mode in self.problem.mode_details[task]
                 if self.problem.mode_details[task][mode].get(resource, 0) > 0
             ]
+            if len(task_modes_consuming) == 0:
+                # when empty, the constraints don't work !
+                return
             fake_task_res = [
                 (
                     model.NewFixedSizeIntervalVar(
@@ -481,6 +484,9 @@ def create_cumulative_constraint_and_resource_capa(
                 for mode in self.problem.mode_details[task]
                 if self.problem.mode_details[task][mode].get(resource, 0) > 0
             ]
+            if len(task_modes_consuming) == 0:
+                # when empty, the constraints don't work !
+                return
             fake_task_res = [
                 (
                     model.NewFixedSizeIntervalVar(