Fix analysis issues

[devoncarew]

• update some pubspec deps
• update one of the examples to null safety

I believe this should address the CI failure.

[pq]

This is great. My sense is that the best way to handle the widget_surveyor errors, is to remove the example. (It's long in the tooth.) I'll follow up on that.

Thanks!

[devoncarew]

This is great. My sense is that the best way to handle the widget_surveyor errors, is to remove the example. (It's long in the tooth.) I'll follow up on that.

👍 , and thanks for the merge (I hadn't seen the analysis errors until now)