fix: handle nullable worlfowTask

liferay-plugins-sdk-6.2/portlets/portos-bo-portlet/docroot/WEB-INF/service/it/tref/liferay/portos/bo/util/WorkflowUtil.java

@@ -256,9 +256,11 @@ public class WorkflowUtil {
 			ControlloPratica controlloPratica) throws PortalException, SystemException {
 
 		WorkflowTask workflowTask = getLastTask(companyId, groupId, null, controlloPratica);
-		Map<String, Serializable> workflowContext = getWorkflowContext(controlloPratica);
-		WorkflowTaskManagerUtil.assignWorkflowTaskToUser(companyId, assegnatoreUserId,
-				workflowTask.getWorkflowTaskId(), istruttoreId, StringPool.BLANK, null, workflowContext);
+		if(workflowTask != null) {
+			Map<String, Serializable> workflowContext = getWorkflowContext(controlloPratica);
+			WorkflowTaskManagerUtil.assignWorkflowTaskToUser(companyId, assegnatoreUserId,
+					workflowTask.getWorkflowTaskId(), istruttoreId, StringPool.BLANK, null, workflowContext);
+		}
 	}
 
 	public static Map<String, Serializable> getWorkflowContext(ControlloPratica controlloPratica)