fix missing plugin test (grid)

Author: fredroy

bindings/Sofa/tests/Core/ForceField.py

@@ -108,6 +108,7 @@ def simulate_beam(linear_solver_template):
 
         root.addObject('DefaultAnimationLoop')
 
+        root.addObject('RequiredPlugin', name='Sofa.Component.Topology.Container.Grid')
         root.addObject('RequiredPlugin', name='Sofa.Component.ODESolver.Backward')
         root.addObject('RequiredPlugin', name='Sofa.Component.LinearSolver.Direct')
         root.addObject('RequiredPlugin', name='Sofa.Component.Engine.Select')