This fixes a number of issues that can or could result in invalid JavaScript search index files, and a single invalid index file breaking the whole JavaDoc search feature.
- The `IndexItem` now throws `IllegalArgumentException` if the label argument contains a line break. This was the original cause for this bug and was already fixed in [JDK-8305407](https://bugs.openjdk.org/browse/JDK-8305407), but it is a good idea to add the explicit check to fail in a visible way should it occur again. - The `IndexItem.escapeQuotes(String)` method now escapes backslashes in addition to quote. Failure to escape a trailing backslash would result in an escaped quote, leading to an invalid index file. - The search script gets a check for null/undefined to avoid a missing tag index file to break the search feature as a whole. Note that the added test covers only the second item in the list above. The other two changes are trivial and would require undue effort to test. ------------- Commit messages: - JDK-8305710: Line breaks in search tags cause invalid JSON in index file Changes: https://git.openjdk.org/jdk/pull/14016/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14016&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8305710 Stats: 75 lines in 4 files changed: 45 ins; 6 del; 24 mod Patch: https://git.openjdk.org/jdk/pull/14016.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/14016/head:pull/14016 PR: https://git.openjdk.org/jdk/pull/14016
