hg: jdk/jdk: 8213956: javadoc crash using {@index} in doc-files file

[jonathan.gibbons at oracle.com]

Changeset: 6d243dcde190
Author:    jjg
Date:      2018-11-26 11:00 -0800
URL:       http://hg.openjdk.java.net/jdk/jdk/rev/6d243dcde190

8213956: javadoc crash using {@index} in doc-files file
Reviewed-by: jlahoda, hannesw, pmuthuswamy

! src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/DocFilesHandlerImpl.java
! src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/HtmlDoclet.java
! src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/TagletWriterImpl.java
+ test/langtools/jdk/javadoc/doclet/testIndexInPackageFiles/TestIndexInPackageFiles.java