Only initialize the KMS config map if env map contains values (#22959)

- This protects against a test in ENT and a use-case in which
   we would force a migration for stored configs that had been
   written with a nil configuration

internalshared/configutil/kms.go

@@ -216,7 +216,7 @@ func configureWrapper(configKMS *KMS, infoKeys *[]string, info *map[string]strin
 	var err error
 
 	envConfig := GetEnvConfigFunc(configKMS)
-	if configKMS.Config == nil {
+	if len(envConfig) > 0 && configKMS.Config == nil {
 		configKMS.Config = make(map[string]string)
 	}
 	// transit is a special case, because some config values take precedence over env vars