InvalidOperationException in PhotonServer 3.4

Hi, I have some problems that I'd like to comment you.

Sometimes, when I am attached in Visual Studio to Photon Server i get an exceptin of the type:

InvalidOperationException: collection was modified enumeration operation may not execute

In LoadBalancing solution (photon server 3.4)
In GameList.cs, function SendGame, calling at peer.SendEvent(eventData, new SendParameters());

Why is occurring this error? Is it usual to have sometimes this error?
It stops the execution because i am debugging , but if i am not debugging the execution continue in Spite of the error?

Should I catch those exceptions or simply mark them to be ignored in visual studio ?

Thank you.