### Godot version

v4.0.beta17.official [c40020513]

### System information

Windows 11, OpenGL (Compatibility), RTX 2060 (31.0.15.2824)

### Issue description

I tried to make a blurred panel for a ui element with texturelod via shader:

```glsl
shader_type canvas_item;

uniform sampler2D SCREEN_TEXTURE : hint_screen_texture, filter_linear_mipmap_anisotropic;
uniform float blur_amount : hint_range(0.0, 5.0);

void fragment() {
	vec4 blurred = textureLod(SCREEN_TEXTURE, SCREEN_UV, blur_amount);
	COLOR = blurred;
}
```

but what I got instead is this:
![image](https://user-images.githubusercontent.com/72286622/217170426-49f6712d-47ef-4c53-b9f1-30d8ad868084.png)

vulkan renderer does not exhibit this issue:
![image](https://user-images.githubusercontent.com/72286622/217170565-a013c712-94f6-49d1-b9ec-091c28a7790b.png)


### Steps to reproduce

1. Add a TextureRect node
2. Add a Panel node to overlay the previously added node
3. Apply the blur shader to the panel node

### Minimal reproduction project

N/A
const RenderTarget *rt = render_target_owner.get_or_null(p_render_target);
	ERR_FAIL_COND_V(!rt, Rect2i());
	return _render_target_get_sdf_rect(rt);
}
void TextureStorage::render_target_mark_sdf_enabled(RID p_render_target, bool p_enabled) {
	RenderTarget *rt = render_target_owner.get_or_null(p_render_target);
	ERR_FAIL_COND(!rt);
	rt->sdf_enabled = p_enabled;
}
bool TextureStorage::render_target_is_sdf_enabled(RID p_render_target) const {
	const RenderTarget *rt = render_target_owner.get_or_null(p_render_target);
	ERR_FAIL_COND_V(!rt, false);
	return rt->sdf_enabled;
}
GLuint TextureStorage::render_target_get_sdf_texture(RID p_render_target) {
	RenderTarget *rt = render_target_owner.get_or_null(p_render_target);
	ERR_FAIL_COND_V(!rt, 0);
	if (rt->sdf_texture_read == 0) {
		Texture *texture = texture_owner.get_or_null(default_gl_textures[DEFAULT_GL_TEXTURE_BLACK]);
		return texture->tex_id;
	}
	return rt->sdf_texture_read;
}
void TextureStorage::_render_target_allocate_sdf(RenderTarget *rt) {