WireMockExtension.stopServerIfRunning() produces NPE when Unit Test aborts unexpectedly

[bertramn]

Proposal

When using WiremockExtension with other JUnit5 extensions, another extension could unexpectedly fail. A failure would lead to wiremock server never to be started BUT JUnit will attempt to clean up all extensions with a call to extension.afterAll(extensionContext). this will trigger WiremockExtension.stopServerIfRunning() and produces a NullPointerException because the wireMockServer has never been initialised. To prevent this from happening a null check should be added like here.

Reproduction steps

Create a test that loads multiple extensions and make sure another extension loaded after the wiremock one fails.

References

No response