You can solder a small guage wire across the broken spot. Use a low wattage soldering iron 25 watts would be a good choice. Dont try to use a higher wattage iron or gun you will burn or melt the circuit board. Just clean the circuit trace copper foil with steel wool or fine sandpaper before you try to solder. if you dont feel like trying it yourself find someone who can solder. also a warning do not use acid core solder or plumbing type solder. you need electronic type solder.
The dash cluster has a single ground wire that has it's own plug. Its separate from all the other cluster wires in the rectangular plug.
That single ground connection branches off (via the printed circuit traces) to ground the gas gauge (or optional in-dash tach), the R/L turn indicator bulbs, high beam indicator bulb, and about 5 bulbs that backlight the cluster.