There is already a post about it in here, but the problem is not solved, in fact it is not a solution to the problem. What can we do to avoid shadows from emission shaders?
There's a similar post about it in here, and still the problem is not solved, and it seems: LIGHT PATHS CANNOT BE USED FOR MESH LIGHTS.
Here is a blend file that contains a simple experiment that demonstrates that the aforementioned solution in the first link does not work:
So, how do we avoid mesh lights to cast shadows?