GridMap accidental error

[2821869675]

Godot version:
3.2.1.srable
Issue description:
Adding a cell after deleting a large number of cells reports an error
Steps to reproduce:
So let's create some blocks:
for x in range(32): for y in range(32): map.set_cell_item(x,0,y,0)
And then delete them:
for x in range(32): for y in range(32): map.set_cell_item(x,0,y,-1)
And then add:
for x in range(32): for y in range(32): map.set_cell_item(x,0,y,0)
The console will have an error at this point

Minimal reproduction project:
demo_Error.zip

[qarmin]

Duplicate of #33648