### Godot version

v4.0 rc6

### System information

Windows 10

### Issue description

When using a ViewportTexture from a SubViewport on a TextureRect, it throws errors after running the scene once and then switching scenes in the editor.
![Pasted image 20230227212626](https://user-images.githubusercontent.com/44676282/221680047-984fa03e-33d1-4856-9a7f-1700b28423cf.png)


### Steps to reproduce

Run the canvas-scene once.
Switch to another scene in the editor.
Switch back to the canvas-scene

### Minimal reproduction project

[ViewportTextureError.zip](https://github.com/godotengine/godot/files/10844099/ViewportTextureError.zip)

gui.drag_data = control->get_drag_data(control->get_global_transform_with_canvas().affine_inverse().xform(mpos - gui.drag_accum));
							if (gui.drag_data.get_type() != Variant::NIL) {
								gui.mouse_focus = nullptr;
								gui.forced_mouse_focus = false;
								gui.mouse_focus_mask.clear();
								break;
							} else {
								Control *drag_preview = _gui_get_drag_preview();
								if (drag_preview) {
									ERR_PRINT("Don't set a drag preview and return null data. Preview was deleted and drag request ignored.");
									memdelete(drag_preview);
									gui.drag_preview_id = ObjectID();
								}
								gui.dragging = false;
							}
							if (control->data.mouse_filter == Control::MOUSE_FILTER_STOP) {
								break;
							}
						}
						if (ci->is_set_as_top_level()) {
							break;
						}
						ci = ci->get_parent_item();
					}
				}
				gui.drag_attempted = true;
				if (gui.dragging) {
					_propagate_viewport_notification(this, NOTIFICATION_DRAG_BEGIN);
				}
			}