This is one of the arguments I never understood. If an enemy invasion fleet is above the planet, the last thing a credit loving smuggler is going to do is try to fight the fleet. At best he will just run the blockade and jet away to some other underworld hub.
You can't spend your credits if you're dead.
The argument is that if a power BLOCKADES Nar Shaddaa, as has been suggested for Traya with her garvity well things, then there'll be backlash. Smugglers can't make credits off the biggest underworld market in the galaxy if they can't leave or enter Nar Shaddaa. They're not gonna sit by and lose money, influence, and favor with the dangerous gang leaders they work for. Trying to interupt the business of the underworld has never ended well for anyone.
And, as GarfieldJL pointed out, if Traya does not activate the gravity wells and everyone escapes, G0-T0 will have the same chance to disappear. (For sure, considering he's invisible already.)