Many bass amps have a DI output (XLR jack), which,
unlike a line out, is actually intended for routing into a live
mixing console. For bass amps which don't have this, it's actually
often best to use an external DI, entirely before the amp.
You also lose preamp sound shaping then, but whether the Pathfinder
actually does anything useful to the sound there... I'd have my
doubts. – In fact, some live engineers prefer putting their own DI
in front of even a high-quality bass amp, because this way they
have better control of how the bass will sit in the mix.
For bass you don't need a top-notch DI, but a decent active one
would be a good investment.
That said, this kind of plug-in-mute switch is indeed a
very simple circuit that you can easily disable
yourself†. It is usually implemented as an extra contact
which doesn't contact the plug, but the T contact – but only if
no cable is plugged in.
†Voids warranty, of course.