RFR: 8253641: Missing newline in PrettyWriter::printClassLoader if classloader is null.

[Michael Bien]

Trivial fix which adds a missing new line to PrettyWriter::printClassLoader if clazz == null.

PrettyWriter is used for both the jfr CLI tool and also for the impl of the public JFR API behind
jdk.jfr.Event::toString().

how to reproduce using JFR CLI:

To generate a JFR dump for testing, simply start HelloWorld.java
public class HelloWorld {
    public static void main(String[] args) {System.out.println("hello there");}
}
with
`jdk-15+36/bin/java -XX:StartFlightRecording=filename=dump.jfr,dumponexit=true HelloWorld.java`


current result for events where the classLoader field equals null (note: newline missing):

jdk-15+36/bin/jfr print --events jdk.ModuleRequire dump.jfr
...
jdk.ModuleRequire {
  startTime = 16:12:43.524
  source = {
    name = "jdk.nio.mapmode"
    version = "15"
    location = "jrt:/jdk.nio.mapmode"
    classLoader = null  }
  requiredModule = {
    name = "java.base"
    version = "15"
    location = "jrt:/java.base"
    classLoader = null  }
}
...

after the patch, using same jfr dump and displaying the same event:

jdk16/build/linux-x86_64-server-release/jdk/bin/jfr print --events jdk.ModuleRequire dump.jfr
...
jdk.ModuleRequire {
  startTime = 16:12:43.524
  source = {
    name = "jdk.nio.mapmode"
    version = "15"
    location = "jrt:/jdk.nio.mapmode"
    classLoader = null
  }
  requiredModule = {
    name = "java.base"
    version = "15"
    location = "jrt:/java.base"
    classLoader = null
  }
}
...

sidenote:

There would be an opportunity to merge the two sequential if-else blocks[1] in printClassLoader over the clazz variable
after this patch, but this would obfuscate the actual bug fix, so I decided to omit it. Let me know if I should add
that. [1]
https://github.com/mbien/jdk/blob/67750e2b599b3f2a6b814d7bceada785ca4051f9/src/jdk.jfr/share/classes/jdk/jfr/internal/tool/PrettyWriter.java#L440-L448

-------------

Commit messages:
 - bugfix: Missing newline in PrettyWriter::printClassLoader if classloader is null.

Changes: https://git.openjdk.java.net/jdk/pull/248/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=248&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253641
  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/248.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/248/head:pull/248

PR: https://git.openjdk.java.net/jdk/pull/248