Merge pull request #1799 from wangliang181230/bugfix-hystrix-RootContext.bind-throw-xid-must-be-not-null

bugfix: fix compatibility issue with 'seata-all-1.4.0'

spring-cloud-alibaba-starters/spring-cloud-starter-alibaba-seata/src/main/java/com/alibaba/cloud/seata/feign/hystrix/SeataHystrixConcurrencyStrategy.java

@@ -36,6 +36,7 @@ import io.seata.core.context.RootContext;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import org.springframework.util.StringUtils;
 import org.springframework.web.context.request.RequestAttributes;
 import org.springframework.web.context.request.RequestContextHolder;
 
@@ -156,11 +157,15 @@ public class SeataHystrixConcurrencyStrategy extends HystrixConcurrencyStrategy
 		public K call() throws Exception {
 			try {
 				RequestContextHolder.setRequestAttributes(requestAttributes);
-				RootContext.bind(xid);
+				if (!StringUtils.isEmpty(xid)) {
+					RootContext.bind(xid);
+				}
 				return actual.call();
 			}
 			finally {
-				RootContext.unbind();
+				if (!StringUtils.isEmpty(xid)) {
+					RootContext.unbind();
+				}
 				RequestContextHolder.resetRequestAttributes();
 			}
 		}