erp5_simulation: Display Divergence dialog even if there is nothing to solve...

erp5_simulation: Display Divergence dialog even if there is nothing to solve (same as legacy Simulation Dialog).

This fixes the following Site Error when there is no Divergence to solve:
  AttributeError: 'NoneType' object has no attribute 'SolverProcess_getSolverDecisionList'

This may happen if user selects 'Solve Divergence' Action and solve
Divergences, then immediately goes back and selects again this action
whereas there is actually no Divergence to solve.

bt5/erp5_simulation/SkinTemplateItem/portal_skins/erp5_simulation/Delivery_getSolverDecisionList.xml

@@ -51,6 +51,9 @@
         <item>
             <key> <string>_body</string> </key>
             <value> <string>solver_process = context.Delivery_getSolverProcess()\n
+if solver_process is None:\n
+  return []\n
+\n
 # XXX should omit \'solved\' decision?\n
 return solver_process.SolverProcess_getSolverDecisionList()\n
 </string> </value>