As you can see you have received differnt and opposite answers. It all depends on what type of 12 charger has been fitted, There are three generic types, and it will depend which country the caravan was built for, and when it was built. I am not sufficiently familiar with Gobur caravans to know exactly which they had.
The oldest and most basic are half or full wave rectified unregulated units. These are basically 2A battery chargers, and must be used with a battery to provide a load and reservoir to enable higher current appliances like water pumps to be used. If used without a battery, the supply might not have enough current capability to run higher capacity products, or other appliance's may not run or could be damaged by the un smoothed output. Another problem is the output is a series of pulses at line or twice line frequency, which will reach a pal voltage of about 21V. If left connected to a battery with current being used for long periods in storage, they will overcharge and permanently damage the battery. Some batteries might explode, I know having had to deal with caravans damaged in this way.
The second type of charger is the same as the first but with a regulator to prevent excessive voltage generation, These are less likely to damage batteries but its not unknown, and they also typically only had a 3 or 5A output.
The third type is called a (linear) DC power supply, and it usually has a greater smoothed output current capacity of 5 to 7A and the output is also clamped to 13.8V, sufficient to charge a battery continually. They can be used without a battery, but they might only run a few lights or may be small water pump. They are better used with a battery
The most recent systems use Switch Mode Power Supply (SMPS) architecture. These don't have a heavy conventional line frequency transformer, instead they use a high frequency converter to keep size and weight and self heating low and to increase efficiency. These can provide much higher regulated output currents, and in many cases are sufficient to run the internal caravan appliance's without a battery.
In the absence of knowing exactly what type of charger/power supply you have already, its impossible to say it would be safe not to fit a battery.