Fix NPE in QuarkusTestExtension.runAfterAllCallbacks() on failed boot (2.2)

[famod]

Basically backports this: fc697fc#diff-462fa0cb443c21c9406c8b4daeb31500f20a4c9b46a0b039adcc93dee6a3bea4R1139

More context can be found in #19982

[famod]

/cc @gsmet because of excplicit backport.

[gsmet]

Thanks for the ping, I attached the version manually.

[quarkus-bot]

Failing Jobs - Building c58e113

Status	Name	Step	Failures	Logs	Raw logs
✖	Gradle Tests - JDK 11 Windows	Build	Failures	Logs	Raw logs
✔️	JVM Tests - JDK 11
✖	JVM Tests - JDK 11 Windows	Build	⚠️ Check →	Logs	Raw logs
✖	JVM Tests - JDK 16	Build	⚠️ Check →	Logs	Raw logs

Full information is available in the Build summary check run.

⚠️ Errors occurred while downloading the build reports. This report is incomplete.

Failures

⚙️ Gradle Tests - JDK 11 Windows #

- Failing: integration-tests/gradle 

📦 integration-tests/gradle

✖ io.quarkus.gradle.devmode.BasicKotlinApplicationModuleDevModeTest.main line 18 - More details - Source on GitHub

org.awaitility.core.ConditionTimeoutException: Condition with lambda expression in io.quarkus.test.devmode.util.DevModeTestUtils that uses java.util.function.Supplier, java.util.function.Supplierjava.util.concurrent.atomic.AtomicReference, java.util.concurrent.atomic.AtomicReferencejava.lang.String, java.lang.Stringboolean was not fulfilled within 1 minutes.
	at org.awaitility.core.ConditionAwaiter.await(ConditionAwaiter.java:166)
	at org.awaitility.core.CallableCondition.await(CallableCondition.java:78)

[famod]

Those two JVM Tests are strangely cut off somehow, but the "JVM Tests - JDK 11" one passed, so...
And BasicKotlinApplicationModuleDevModeTest failed before, so it seems you fix was not enough @gsmet

Good to merge I think, any objections?