Attempt to fix/log exception in turret target acquisition.

Fixed new grid work task being fired off while the previous task was still running.

Fixed exception caused by trying to cast wrong type of packet.

Actually fixed exception in client weld/grind code causing thread usage to spiral out of control.

Tried to fix exception in client weld/grind code causing thread usage to spiral out of control.

- Fixed potential hang on world close.
- Fixed welders with `WorkRate > 4` getting "stuck" and failing to continue working.