Steps to reproduce:
1) Navigate to Administration->General->Geographical maps.
2) Set Tile provider - Other.
Tile URL - anything
Attribution HTM l - anything.
Max zoom level - 10.
3) Press Update button.
4) Change Tile provider to OpenStreetMap (or another one, no matter what). And then again to Other.

Result:
All fields are empty.

Expected:
All fields are saved and correctly filled.