fix: handle void safety on workflowTask assignment in GestioneAttivitaPortlet

liferay-plugins-sdk-6.2/portlets/portos-bo-portlet/docroot/WEB-INF/src/it/tref/liferay/portos/bo/portlet/GestioneAttivitaPortlet.java

@@ -188,9 +188,11 @@ public class GestioneAttivitaPortlet extends MVCPortlet {
 					default:
 						break;
 				}
+				if(Validator.isNotNull(role)){
 					WorkflowTaskManagerUtil.assignWorkflowTaskToRole(controlloPratica.getCompanyId(),
 							serviceContext.getUserId(), workflowTaskId, role.getRoleId(), StringPool.BLANK, null,
 							WorkflowUtil.getWorkflowContext(controlloPratica));
+				}
 			} else {
 				throw new SystemException("riassegnare al ruolo non possibile");
 			}