Fill null cells with selected data

Hi,

I have to set a Class for each User & Channel in Power Query. I have created a Column that assign a class for the first Channel in pipeline (1487). Now, I'd like to set the same class to other Channels for the same user. I have tryed grouping the data, it was close, but I didn't managed to get the correct answer. Fill also didn't worked because the data in my table is not consecutive and we have no option to sort the data by 2 tables simultaneously . 

Here you have a data sample:

I'd like to have the nulls populated with the data which is shown for Channel 1487 for each user.

Any suggestions will be much appreciated.