i was messing around with open simplex noise and i had functional code but when i restart the project (after 4 or 5 attempts) it says "invalid type in function "set_cell" in base "tilemap". cannor convert argument 3 from nil to int"

```
extends Node2D
var mapsize = Vector2()
const minsize = 100
const maxsize = 250
var currentseed
var generator = RandomNumberGenerator.new()
var terrain = {
"water" : 0,
"sand" : 1,
"dirt" : 2,
"grass" : 3,
"mountain" : 4,
"snow" : 5,
"deepwater" : 6
}
var noise
func RNG():
generator.randomize()
currentseed = generator.get_seed()
func mapsizegen():
randomize()
mapsize.x = generator.randi_range(minsize, maxsize)
mapsize.y = generator.randi_range(minsize, maxsize)
func deepwatergen():
for a in mapsize.x + 20:
for b in mapsize.y + 20:
$tilemap.set_cell(a + 20, b + 20, terrain.deepwater)
func watergen():
for c in mapsize.x + 10:
for d in mapsize.y + 10:
$tilemap.set_cell(c + 25, d + 25, terrain.water)
func sandgen():
for e in mapsize.x + 4:
for f in mapsize.y + 4:
$tilemap.set_cell(e + 28, f + 28, terrain.sand)
func mapgen():
for g in mapsize.x:
for h in mapsize.y:
$tilemap.set_cell(g + 30, h + 30,
_get_tile_index(noise.get_noise_2d(float(g), float(h))))
func _get_tile_index(noise_sample):
if noise_sample < -0.4:
return terrain.water
if noise_sample < -0.2:
return terrain.sand
if noise_sample < -0.1:
return terrain.dirt
if noise_sample < 0.4:
return terrain.grass
if noise_sample < 0.6:
return terrain.mountain
if noise_sample < 0.8:
return terrain.snow
func _ready():
RNG()
mapsizegen()
deepwatergen()
watergen()
sandgen()
randomize()
noise = OpenSimplexNoise.new()
noise.seed = currentseed
noise.octaves = 2
noise.period = 10
noise.lacunarity = 1
noise.persistence = 0.75
mapgen()
```

it shows the error at:

```
$tilemap.set_cell(g + 30, h + 30,
_get_tile_index(noise.get_noise_2d(float(g), float(h))))
```

i used set_cellv too but is the same