Recent JDK 27 EA builds of javac are crashing on the following program.

The following program has an error (the symbol NoSuch isn't defined), which should be reported as a diagnostic instead of causing a crash.

```
import static java.util.stream.Collectors.toSet;

import java.io.Serializable;
import java.util.Set;
import java.util.stream.Stream;

abstract class Z {
  Supplier<Set<String>> f() {
    return g(
        s -> Stream.of(NoSuch.NAMES.stream(), Stream.of("hello")).flatMap(i -> i).collect(toSet()));
  }

  abstract <T> Supplier<T> g(Supplier<T> f);
}

interface Supplier<T> extends Serializable {
  T get(VisitorState state);
}

class VisitorState {
  String getName(String s);
}
```

$ javac -fullversion Z.java
...
java.lang.AssertionError: isSubtype PACKAGE
        at jdk.compiler/com.sun.tools.javac.code.Types$4.visitType(Types.java:1129)
        at jdk.compiler/com.sun.tools.javac.code.Types$4.visitType(Types.java:1106)
        at jdk.compiler/com.sun.tools.javac.code.Types$DefaultTypeVisitor.visitPackageType(Types.java:4981)
        at jdk.compiler/com.sun.tools.javac.code.Type$PackageType.accept(Type.java:1592)
        at jdk.compiler/com.sun.tools.javac.code.Types$DefaultTypeVisitor.visit(Types.java:4976)
        at jdk.compiler/com.sun.tools.javac.code.Types.isSubtype(Types.java:1102)
        at jdk.compiler/com.sun.tools.javac.code.Types.isSubtype(Types.java:1073)
        at jdk.compiler/com.sun.tools.javac.comp.Check.checkAccessFromSerializableElementInner(Check.java:2900)
        at jdk.compiler/com.sun.tools.javac.comp.Check.checkAccessFromSerializableElement(Check.java:2882)

This appears to be a regression since JDK 25, the JDK 25 javac reports the following diagnostics:

javac full version "25.0.2+10-69"
T.java:10: error: package NoSuch does not exist
        s -> Stream.of(NoSuch.NAMES.stream(), Stream.of("hello")).flatMap(i -> i).collect(toSet()));
                             ^
T.java:21: error: missing method body, or declare abstract
  String getName(String s);
         ^
2 errors