Fixes a crash when moving items to a full inventory.
When moving a stack to a particular slot inventory, if the inventory
was full from that slot to the end of the inventory, the add() method
would call itself recursively with the same parameters, leading to
infinite recursion and a Java crash due to stack overflow.  I believe
my patch is probably the originally intended code; I tested that it
would not crash in a situation where the original code would crash.
Avoid crash that came from calling queueEvent() on detached computer.
Several times, I've gotten a Minecraft crash due to
BaseManager.queueEvent(...) calling IComputerAccess.queueEvent(...)
with a detached computer.  After making this change, I haven't gotten
the crash since.  (Technically, the code still has a race condition,
between checking our computers map and calling queueEvent(...);
but the window is much, much shorter now.)