Fix NPE in spring-mvc

[SylvainJuge]

What does this PR do?

Fixes NPE when the spring mvc view name is null.
This is triggered when with opbeans-java with a simple curl http://localhost:8080/

java.lang.NullPointerException
        at co.elastic.apm.agent.impl.transaction.AbstractSpan.appendToName(AbstractSpan.java:331)
        at co.elastic.apm.agent.impl.transaction.AbstractSpan.appendToName(AbstractSpan.java:327)
        at co.elastic.apm.agent.springwebmvc.ViewRenderInstrumentation$ViewRenderAdviceService.beforeExecute(ViewRenderInstrumentation.java:72)
        at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:307)
        ....

• This is a bugfix
  • I have updated CHANGELOG.asciidoc
  • I have added tests that would fail without this fix

[github-actions]

/test

[apmmachine]

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• Start Time: 2022-12-01T10:37:18.343+0000

• Duration: 62 min 50 sec

Test stats 🧪

Test	Results
Failed	0
Passed	3228
Skipped	40
Total	3268

💚 Flaky test report

Tests succeeded.

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