Fix missing @ConditionalOnBean

See spring-projectsgh-30156

Author: mhalbritter

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/TracingAutoConfiguration.java

@@ -18,13 +18,15 @@
 
 import java.util.List;
 
+import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.observation.Observation.GlobalTagsProvider;
 import io.micrometer.core.instrument.observation.ObservationHandler;
 import io.micrometer.core.instrument.observation.ObservationPredicate;
 import io.micrometer.tracing.handler.TracingObservationHandler;
 
 import org.springframework.boot.autoconfigure.AutoConfiguration;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.context.annotation.Bean;
@@ -39,6 +41,7 @@
  * @since 3.0.0
  */
 @AutoConfiguration(after = CompositeMeterRegistryAutoConfiguration.class)
+@ConditionalOnBean(MeterRegistry.class)
 @ConditionalOnClass(TracingObservationHandler.class)
 public class TracingAutoConfiguration {