Unlike version 2.0rc11, in version 2.1.3 the class MemoryObject hasn't equals() method. In this way getOrAddSafe() add always the object even if the object is already in the map, se we have memory leak.

In my opinion you need to reintroduce the following method:
public boolean equals(Object obj) {
        if(this == obj) { return true; }
        if(obj instanceof MemoryObject) {
            MemoryObject m = (MemoryObject) obj;
            return addr == m.addr && size == m.size ;
        }
        return false;
}