Hi guys and happy new year!
I was so excited about your latest update (today I tried to install EM 5.6.2) that I tried to install it and tested it on some of my projects to see if there were any problems.
Unfortunately I noticed something a little annoying about the behavior of the action in question, which creates a bit of problems for me. Now I'm using EM 5.5.0.15.
As you can see from the following attachment, I have a starting table that has a certain set of data... this table can sometimes happen to be empty.
After the matching database rows action, the schema changes, so that, if in other derived tables in which I carry out a merge operation to perform other operations referring to the current one, the merge action does not give me an error because as output (from matching database rows) I have the structure I select from the database.
Using the new version instead, if the starting table for which I have to do a matching database rows is empty, this action returns the error: object reference not set to an instance of an object.
I also tried to put a block that skips the action when the previous table is empty, but I need the database structure otherwise all the merge actions that I cascade on the project fail.
Is this all desired behavior or can I hope you correct the problem? 
Thank you!