Fixed base which had inverted faces

Another user tried to print the FmGDwP_MGD-20_pot_NEW.stl and found he had problems. I reviewed the design and discovered it had inverted faces which the Cura slicer fixed by filling in the center making the model useless. This remix corrects this problem. The model also has some non-manifold edges which the creator should correct, however they do not interfere with the slicing of the model in this case