You should add a separate check for $product/value != empty, for example by adding an exclusive split before checking if the value is > 0.
Even if the object is not empty, the value of an attribute within the object could still be empty, causing the error message..
I noticed that the case is different: $Product and $product/value. Is your variable $Product or all lower case?
More general:
You could leave the if out and combine the two conditions into one:
$Product !=empty and $Product/value > 0
This will result in true or false. If $Product is empty, the remainder of the expression will not be evaluated.
Mugilan, can you share the microflow with us using the Modeler's microflow share button? So we can see if we can reproduce it.
I think I reproduced what you said in https://modelshare.mendix.com/models/fbb222cc-bc59-401d-b9b4-b3c41d387da5/forumquestion-88178.
My conclusion is same as Joost's, that this: error is thrown because $Product/value is empty.
See the proposed solution: https://modelshare.mendix.com/models/c935f057-1495-4a43-acde-ff92384b8d3d/forum-question-88178-possible-solution