### Godot version

0810ecaafdbee3ea747219e6ab3a8de5d2216a09

### System information

Windows 11, Nvidia 3000, firefox

### Issue description

Exporting the gltf file is corrupt in blender.

### Steps to reproduce

1. Open project.
2. Export as glb
3. Open in blender
4. Blender display many warnings

![image](https://user-images.githubusercontent.com/32321/216740742-de662c5c-f5c3-44b5-a36e-8ad33defdbba.png)


### Minimal reproduction project

https://cdn.discordapp.com/attachments/598003845657788438/1071249610896580691/Test_Game_Project.zip


num_channels = 3;
							break;
						case Mesh::ARRAY_CUSTOM_RGBA_FLOAT:
							num_channels = 4;
							break;
					}
					int texcoord_i = 2 + 2 * custom_i;
					String gltf_texcoord_key;
					for (int prev_texcoord_i = 0; prev_texcoord_i < texcoord_i; prev_texcoord_i++) {
						gltf_texcoord_key = vformat("TEXCOORD_%d", prev_texcoord_i);
						if (!attributes.has(gltf_texcoord_key)) {
							Vector<Vector2> empty;
							empty.resize(vertex_num);
							attributes[gltf_texcoord_key] = _encode_accessor_as_vec2(p_state, empty, true);
						}
					}
					LocalVector<Vector2> first_channel;
					first_channel.resize(vertex_num);
					LocalVector<Vector2> second_channel;
					second_channel.resize(vertex_num);
					for (int32_t vert_i = 0; vert_i < vertex_num; vert_i++) {
						float u = a[vert_i * num_channels + 0];
						float v = (num_channels == 1 ? 0.0f : a[vert_i * num_channels + 1]);
						first_channel[vert_i] = Vector2(u, v);
						u = 0;
						v = 0;
						if (num_channels >= 3) {
							u = a[vert_i * num_channels + 2];
							v = (num_channels == 3 ? 0.0f : a[vert_i * num_channels + 3]);
							second_channel[vert_i] = Vector2(u, v);