NPE when disabling OpenTelemetry

[jamesnetherton]

Describe the bug

Something observed on the nightly Camel Quarkus builds with Quarkus 999-SNAPSHOT. We have a test where otel is disabled with quarkus.otel.enabled = false. The application fails to start due to:

java.lang.RuntimeException: Failed to start quarkus
    at io.quarkus.runner.ApplicationImpl.doStart(Unknown Source)
    at io.quarkus.runtime.Application.start(Application.java:101)
    at io.quarkus.runtime.ApplicationLifecycleManager.run(ApplicationLifecycleManager.java:111)
    at io.quarkus.runtime.Quarkus.run(Quarkus.java:71)
    at io.quarkus.runtime.Quarkus.run(Quarkus.java:44)
    at io.quarkus.runtime.Quarkus.run(Quarkus.java:124)
    at io.quarkus.runner.GeneratedMain.main(Unknown Source)
    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:568)
    at io.quarkus.bootstrap.runner.QuarkusEntryPoint.doRun(QuarkusEntryPoint.java:62)
    at io.quarkus.bootstrap.runner.QuarkusEntryPoint.main(QuarkusEntryPoint.java:33)
Caused by: java.lang.NullPointerException: Cannot invoke "io.smallrye.config.ConfigValue.getValue()" because "value" is null
    at io.quarkus.opentelemetry.runtime.config.OTelFallbackConfigSourceInterceptor.getValue(OTelFallbackConfigSourceInterceptor.java:46)
    at io.smallrye.config.SmallRyeConfigSourceInterceptorContext.proceed(SmallRyeConfigSourceInterceptorContext.java:20)
    at io.smallrye.config.SecretKeysHandlerConfigSourceInterceptor.getValue(SecretKeysHandlerConfigSourceInterceptor.java:26)
    at io.smallrye.config.SmallRyeConfigSourceInterceptorContext.proceed(SmallRyeConfigSourceInterceptorContext.java:20)
    at io.smallrye.config.FallbackConfigSourceInterceptor.getValue(FallbackConfigSourceInterceptor.java:24)
    at io.smallrye.config.SmallRyeConfigSourceInterceptorContext.proceed(SmallRyeConfigSourceInterceptorContext.java:20)
    at io.smallrye.config.SmallRyeConfig.getConfigValue(SmallRyeConfig.java:382)
    at io.quarkus.runtime.configuration.ConfigRecorder.handleConfigChange(ConfigRecorder.java:43)
    at io.quarkus.deployment.steps.ConfigGenerationBuildStep$checkForBuildTimeConfigChange1532146938.deploy_4(Unknown Source)
    at io.quarkus.deployment.steps.ConfigGenerationBuildStep$checkForBuildTimeConfigChange1532146938.deploy(Unknown Source)
    ... 13 more

I see the same thing if I generate a basic app (E.g just with quarkus-otel & no Camel involved) from code.quarkus.io and tweak the Quarkus version to 999-SNAPSHOT.

Expected behavior

OpenTelemetry is disabled as expected without any issues.

Actual behavior

An NPE is thrown (see above stack trace).

How to Reproduce?

1. Create an empty application
2. Set the Quarkus version to 999-SNAPSHOT
3. Add a dependency for quarkus-opentelemetry
4. Disable otel in àpplication.propertieswithquarkus.otel.enabled = false`
5. Package the application and execute the runnable JAR

Output of uname -a or ver

No response

Output of java -version

No response

Quarkus version or git rev

No response

Build tool (ie. output of mvnw --version or gradlew --version)

No response

Additional information

No response

[quarkus-bot]

/cc @brunobat (opentelemetry), @radcortez (opentelemetry)