求助，thymeleaf判断空对象问题

[pppppap]

<label class="label">授课教师</label>
        <p class="content" id="teacher">
            <span th:if="${course!=null}"
                  th:each="i:${course.teachers}"
                  th:text="${i}+'<br>'">
            </span>
        </p>

如果后台传过来的是一个空对象怎么办啊，这样会报错，一直找不到解决方法。
Caused by: org.attoparser.ParseException: Exception evaluating SpringEL expression: "course.teachers" (template: "index" - line 126, col 19)
at org.attoparser.MarkupParser.parseDocument(MarkupParser.java:393) ~[attoparser-2.0.4.RELEASE.jar:2.0.4.RELEASE]
at org.attoparser.MarkupParser.parse(MarkupParser.java:257) ~[attoparser-2.0.4.RELEASE.jar:2.0.4.RELEASE]
at org.thymeleaf.templateparser.markup.AbstractMarkupTemplateParser.parse(AbstractMarkupTemplateParser.java:230) ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]
... 52 common frames omitted

[静坐墙角待红杏]

<span th:if="${course}" th:each="i:${course.teachers}" th:text="${i}+'<br>'"> </span> 空就是false

[卡哇伊qingqing]

想办法不要让course为空. 比如: 写入0或1

[superdaojian]

再加一个判断呗：

<span th:if="${course!=null and course.teachers!=null}"
                  th:each="i:${course.teachers}"
                  th:text="${i}+'<br>'">
            </span>

[OnlyLove_longshao]

<span th:each="i:${course?.teachers}"
                  th:text="${i}+'<br>'">
            </span>

给需要判断的对象加一个问号就可以！

[Ravic-xiao]

这种写法最便捷，感谢