Eliminated DestroyWorkflowThreadError ERROR when signal handler is blocked (#200)

Author: mfateev

src/main/java/com/uber/cadence/internal/sync/POJOWorkflowImplementationFactory.java

@@ -297,6 +297,8 @@ public void processSignal(String signalName, byte[] input, long eventId) {
         Throwable targetException = e.getTargetException();
         if (targetException instanceof DataConverterException) {
           logSerializationException(signalName, eventId, (DataConverterException) targetException);
+        } else if (targetException instanceof Error) {
+          throw (Error)targetException;
         } else {
           throw new Error(
               "Failure processing \"" + signalName + "\" at eventID " + eventId, targetException);

src/test/java/com/uber/cadence/workflow/WorkflowTest.java

@@ -1217,6 +1217,7 @@ public void execute() {
 
     @Override
     public void signal(String value) {
+      Workflow.sleep(Duration.ofSeconds(1));
       signal.complete(value);
     }
   }