can't upload image in using github uploader,appear HttpError: content is not valid Base64

[left0ver]

Description

• Can you reproduce the issue?

Steps to reproduce

1. set image uploader with github
2. copy a image
3. paste in editor and can't upload image

Expected behavior:
upload image correctly

Actual behavior:
can't upload image

Link to an example: [optional]

Versions

• MarkText version: 0.17.1
• Operating system: mac os