DUBBO-454 支持字节流泛化调用

dubbo-config/dubbo-config-api/src/main/java/com/alibaba/dubbo/config/AbstractReferenceConfig.java

@@ -80,7 +80,7 @@ public abstract class AbstractReferenceConfig extends AbstractInterfaceConfig {
 
     @Parameter(excluded = true)
     public Boolean isGeneric() {
-        return ProtocolUtils.isGeneric(generic);
+        return getGeneric() == null ? null : ProtocolUtils.isGeneric(getGeneric());
     }
 
     public void setGeneric(Boolean generic) {