The following malformed @link tag crashes javac with -Xdoclint enabled.

It appears to be a regression in JDK 9.

```
/** {@link double.NAN} */
public class T {}
```

$ javac -fullversion
javac full version "26-ea+22-2263"

$ javac -Xdoclint T.java
An exception has occurred in the compiler (26-ea). Please file a bug against the Java compiler via the Java bug reporting page (https://bugreport.java.com) after checking the Bug Database (https://bugs.java.com) for duplicates. Include your program, the following diagnostic, and the parameters passed to the Java compiler in your report. Thank you.
com.sun.tools.javac.util.ClientCodeException: java.lang.NullPointerException: Cannot read field "kind" because "site" is null
        at jdk.compiler/com.sun.tools.javac.api.ClientCodeWrapper$WrappedTaskListener.started(ClientCodeWrapper.java:869)
        at jdk.compiler/com.sun.tools.javac.api.MultiTaskListener.started(MultiTaskListener.java:120)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.attribute(JavaCompiler.java:1352)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:982)
        at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:319)
        at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:178)
        at jdk.compiler/com.sun.tools.javac.Main.compile(Main.java:66)
        at jdk.compiler/com.sun.tools.javac.Main.main(Main.java:52)
Caused by: java.lang.NullPointerException: Cannot read field "kind" because "site" is null
        at jdk.compiler/com.sun.tools.javac.comp.Attr$IdentAttributer.visitMemberSelect(Attr.java:378)
        at jdk.compiler/com.sun.tools.javac.comp.Attr$IdentAttributer.visitMemberSelect(Attr.java:374)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCFieldAccess.accept(JCTree.java:2593)
        at jdk.compiler/com.sun.tools.javac.comp.Attr.attribIdent(Attr.java:370)
        at jdk.compiler/com.sun.tools.javac.comp.Attr.attribIdent(Attr.java:362)
        at jdk.compiler/com.sun.tools.javac.api.JavacTrees.attributeDocReference(JavacTrees.java:430)
        at jdk.compiler/com.sun.tools.javac.api.JavacTrees.getElement(JavacTrees.java:345)
        at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.visitReference(Checker.java:1007)
        at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.visitReference(Checker.java:119)