EmptyTagTest throws occasionally for IndexOutOfBoundsException when file based log4j2 xml is used

[StrongestNumber9]

Describe the bug

[ERROR] Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.025 s <<< FAILURE! -- in com.teragrep.cfe_35.router.EmptyTagTest
[ERROR] com.teragrep.cfe_35.router.EmptyTagTest.sendEmptyTag -- Time elapsed: 0.017 s <<< ERROR!
java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
        at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
        at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
        at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:266)
        at java.base/java.util.Objects.checkIndex(Objects.java:361)
        at java.base/java.util.ArrayList.get(ArrayList.java:427)
        at com.teragrep.cfe_35.router.EmptyTagTest.sendEmptyTag(EmptyTagTest.java:181)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:569)
        at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:688)
        at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
        at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)

Expected behavior

It doesn't crash

How to reproduce

Used this log4j2.xml

<?xml version="1.0" encoding="UTF-8" ?>
<Configuration>
  <Appenders>
    <Console name="STDOUT">
      <PatternLayout pattern="%d{dd.MM.yyyy HH:mm:ss.SSS} [%level] [%logger] [%thread] %msg%ex%n" />
    </Console>
    <File name="FileOutput" fileName="debug.log">
      <PatternLayout pattern="%d{dd.MM.yyyy HH:mm:ss.SSS} [%level] [%logger] [%thread] %msg%ex%n" />
    </File>
  </Appenders>
  <Loggers>
    <Logger name="com.teragrep.net_01" level="debug" additivity="false">
      <AppenderRef ref="FileOutput"/>
    </Logger>
    <Root level="debug">
      <AppenderRef ref="FileOutput"/>
    </Root>
  </Loggers>
</Configuration>

Then run until crash
while true; do rm -f debug.log; mvn clean package || break; done;

Screenshots

Software version

Commit 88ff40b9086c0d02db7a7a85e5158bff6b763b23 of branch to-9 from kortemik/cfe_35

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Additional context