fix 修复 办理任务时未传参数，导致执行任务无法获取到任务参数的问题

ruoyi-modules/ruoyi-workflow/src/main/java/org/dromara/workflow/domain/bo/CompleteTaskBo.java

@@ -65,13 +65,13 @@ public class CompleteTaskBo implements Serializable {
 
     /**
      * 扩展变量(此处为逗号分隔的ossId)
-     * @return
      */
     private String ext;
 
     public Map<String, Object> getVariables() {
         if (variables == null) {
-            return new HashMap<>(16);
+            variables = new HashMap<>(16);
+            return variables;
         }
         variables.entrySet().removeIf(entry -> Objects.isNull(entry.getValue()));
         return variables;