NullPointerException in LazyTracingSpanContextSupplier when TraceContext.sampled() returns null

[wilkinsona]

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.lang.Boolean.booleanValue()" because the return value of "io.micrometer.tracing.TraceContext.sampled()" is null
	at org.springframework.boot.actuate.autoconfigure.tracing.prometheus.PrometheusExemplarsAutoConfiguration$LazyTracingSpanContextSupplier.isSampled(PrometheusExemplarsAutoConfiguration.java:83)
	at io.prometheus.client.exemplars.DefaultExemplarSampler.doSample(DefaultExemplarSampler.java:46)
	at io.prometheus.client.exemplars.DefaultExemplarSampler.sample(DefaultExemplarSampler.java:34)
	at io.micrometer.prometheus.PrometheusCounter.updateExemplar(PrometheusCounter.java:79)
	at io.micrometer.prometheus.PrometheusCounter.increment(PrometheusCounter.java:58)
	at io.micrometer.core.instrument.Counter.increment(Counter.java:38)
	at io.micrometer.core.instrument.binder.logging.MetricsTurboFilter.decide(LogbackMetrics.java:196)
	at ch.qos.logback.classic.spi.TurboFilterList.getTurboFilterChainDecision(TurboFilterList.java:49)
	at ch.qos.logback.classic.LoggerContext.getTurboFilterChainDecision_0_3OrMore(LoggerContext.java:251)
	at ch.qos.logback.classic.Logger.filterAndLog_0_Or3Plus(Logger.java:375)
	at ch.qos.logback.classic.Logger.log(Logger.java:780)
	at org.apache.commons.logging.LogAdapter$Slf4jLocationAwareLog.warn(LogAdapter.java:444)
	at org.springframework.boot.SpringApplication.handleRunFailure(SpringApplication.java:792)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:321)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1302)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1291)
	at com.example.demo.Gh33070Application.main(Gh33070Application.java:13)