Is EA trading safe?

Depends on what you mean by safe.

Depends on the EA

If you mean

are you guaranteed to earn profits with an EA

No, definitely no. 

An Expert Adviser is a piece of software written specifically for the Meta trader platform. An Expert Adviser can just advise traders which trades to make or can be programmed to automatically execute the trades on a live account. So it is totally depends on the EA weather it is safe or not. 

If you want to get really technical, Forex trading itself, and in fact many other types of trading are not "safe" just by themselves.  What makes a specific trading strategy (and by extension a certain EA) safe or not is the level of money management implemented.  As has been said ("printed") on so many disclaimers ad naseum is "trading contains inherent risks" and "past results is no guarantee of future results".