add miss-deleted snippet from #2956 (#4137)

Author: chickenlj

dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/AppResponse.java

@@ -17,6 +17,7 @@
 package org.apache.dubbo.rpc;
 
 import java.io.Serializable;
+import java.lang.reflect.Field;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.function.Function;
@@ -64,6 +65,23 @@ public AppResponse(Throwable exception) {
     @Override
     public Object recreate() throws Throwable {
         if (exception != null) {
+            // fix issue#619
+            try {
+                // get Throwable class
+                Class clazz = exception.getClass();
+                while (!clazz.getName().equals(Throwable.class.getName())) {
+                    clazz = clazz.getSuperclass();
+                }
+                // get stackTrace value
+                Field stackTraceField = clazz.getDeclaredField("stackTrace");
+                stackTraceField.setAccessible(true);
+                Object stackTrace = stackTraceField.get(exception);
+                if (stackTrace == null) {
+                    exception.setStackTrace(new StackTraceElement[0]);
+                }
+            } catch (Exception e) {
+                // ignore
+            }
             throw exception;
         }
         return result;