prefer_is_not_empty

Use 'isNotEmpty' rather than negating the result of 'isEmpty'.

The analyzer produces this diagnostic when the result of invoking Iterable.isEmpty or Map.isEmpty is negated.

The following code produces this diagnostic because the result of invoking Iterable.isEmpty is negated:

void f(Iterable<int> p) => !p.isEmpty ? p.first : 0;

Rewrite the code to use isNotEmpty:

void f(Iterable<int> p) => p.isNotEmpty ? p.first : 0;