Null-aware operator with cascade doesn't work with newlines?

Following code works:

```dart
void main() {
int? x;
x?..abs()..ceil()..floor();
}
```

This code gives an error:

```dart
void main() {
int? x;
x? // <- Conditions must have a static type of 'bool' - line 3
..abs()
..ceil()
..floor();
}
```

Start by comparing the two Dart snippets and reproducing the diagnostic for the newline-separated cascade. Read the language specification sections covering null-aware operators and cascades, then determine whether the newline form should have the same meaning as the one-line form; done means the expected behavior is specified and verified.

Written by the indexing model from the issue text.