Do not wrap error if multierror does not have one. (#3772)

CHANGELOG.md

@@ -49,6 +49,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Remove use of deprecated `"math/rand".Seed` in `go.opentelemetry.io/otel/example/prometheus`. (#3733)
 - Do not silently drop unknown schema data with `Parse` in  `go.opentelemetry.io/otel/schema/v1.1`. (#3743)
 - Data race issue in OTLP exporter retry mechanism. (#3756)
+- Fixes wrapping a nil error in some cases (#????)
 
 ## [1.13.0/0.36.0] 2023-02-07
 

sdk/metric/pipeline.go

@@ -551,6 +551,9 @@ func (m *multierror) errorOrNil() error {
 	if len(m.errors) == 0 {
 		return nil
 	}
+	if m.wrapped == nil {
+		return errors.New(strings.Join(m.errors, "; "))
+	}
 	return fmt.Errorf("%w: %s", m.wrapped, strings.Join(m.errors, "; "))
 }