在GridView.count（）中，在null上调用了getter'length'

Question

我在Consumer（）中实现了GridView.count并收到以下错误：exp

但是当我尝试打印列表长度时，它不是null。

The getter 'length' was called on null.

这是我的代码：

I/flutter ( 6581): 7

════════ Exception caught by widgets library ═══════════════════════════════════
The following NoSuchMethodError was thrown building NotificationListener<KeepAliveNotification>:
The getter 'length' was called on null.
Receiver: null
Tried calling: length

如何解决此问题？即使长度不为null。

注意：此问题是由另一个API调用引起的，该API返回null且未正确处理。