Updating Row SQLSERVER

Hi, I am updating a table with the elements I show you below:

I am updating 4 those rows with my job:

As you can see, I have an infinite loop which is updating all the time the rows I showed you before. I am doing this fine with mysqlserverinput connection, using the option : "update".

MY PROBLEM is that I am updating all the time, even when I have no values. What I want to do is doing a condition that just updates a row when I have some values in there.  For example, If I have

id_machine=123 

I want it to remains "123" until I have some value to add, not when I have "blank or null".