AssertionError trying to import object sprite (SKYTEMPLE-8E)

[theCapypara]

Under unknown circumstances, importing object sprites may fail, showing this error:

AssertionError: null
  File "module\sprite\controller\object.py", line 95, in on_importimage_clicked
  File "module\sprite\module.py", line 100, in save_object_sprite

Automatic via sentry. 175 reports. First: 1.3.8rc3, Last: 1.5.4

[sentry-io]

Sentry issue: SKYTEMPLE-8E

[Chesyon]

I can consistently reproduce this error. Trying to import an image for an object sprite fails when trying to do so directly after creating the object sprite. Once the ROM is reloaded, the error goes away.