Loop and merge based on embedded data field from web service

Hello, 

I am providing some sample products for my customers to taste.
 

The customers and each will select up to 5 and will get the survey to rate them.

I retrieve those products through a webservice which then feeds the embedded data (product name).

 I set the embedded data in the begining of the survey flow  with product names as Product_Name1, Product_Name2 etc.

Then I map those embedded data from the webservice as below: (url is empty for now, I will do the testing later) 

The questions will be the same for each product so I will use Loop&Merge functionality.

However, when I set the loop&merge based on the embedded data and as the customer might choose less than 5 products, I don’t know how to stop loop&merge if the embedded data turns empty. For example, if the customer chooses 3 products, Product_Name4 and Product_Name5 will be empty and I want to stop the loop after the 3rd time. 

Is there any way to set a condition in the survey flow to stop when the embedded data is empty by using the loop&merge functionality ? Or is there any custom code to make it happen?

Thanks in advance.