No, that is not a concern anymore than an antimatter or warp core containment breach on a ship without extra tanks is.Say is there a possible downside of having the extra antimatter being that this is suppose to be a combat vessel, so extra antimatter means this ship would explode when its taken down.
Although its a big hefty craft with lots of shields so its moot but still.
The biggest potential antimatter risk factor is probably the neutronic fuel storage tank, since it sits in a cargo bay and is likely a bit more difficult to simply eject, in addition to providing a larger profile.