changelog: point AppenderDynamicMBean fix at apache#4185

Folded from closed apache#4219 per review request; both JMX null-guards ship here.

Signed-off-by: Sebastien Tardif <sebtardif@ncf.ca>

Author: SebTardif

src/changelog/.2.x.x/fix_appender_dynamic_mbean_null_layout.xml

@@ -3,6 +3,6 @@
        xmlns="https://logging.apache.org/xml/ns"
        xsi:schemaLocation="https://logging.apache.org/xml/ns https://logging.apache.org/xml/ns/log4j-changelog-0.xsd"
        type="fixed">
-  <issue id="TBD" link="https://github.com/apache/logging-log4j2/pull/TBD"/>
+  <issue id="4185" link="https://github.com/apache/logging-log4j2/pull/4185"/>
   <description format="asciidoc">Fix NPE in log4j-1.2-api `AppenderDynamicMBean.setLayout` when the layout class cannot be instantiated</description>
 </entry>