【kotlin】报错 Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type List?

报错如下：

【kotlin】报错 Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type List<String>?

解决如下：

【kotlin】报错 Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type List<String>?

另一种情况：

【kotlin】报错 Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type List<String>?

解决如下：

【kotlin】报错 Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type List<String>?