KeyError at /media/* 'content-type' every alternate response

[raiaman15]

If a page contains any media file, or if we open media files in development (DEBUG=True), every second response shows this error.
Am I doing something wrong?

Console Output:
web_1 | [26/Dec/2020 09:08:39] "GET /media/1.png HTTP/1.1" 200 6440
web_1 | Internal Server Error: /media/1.png
web_1 | Traceback (most recent call last):
web_1 | File "/usr/local/lib/python3.9/site-packages/django/core/handlers/exception.py", line 34, in inner
web_1 | response = get_response(request)
web_1 | File "/usr/local/lib/python3.9/site-packages/livesync/core/middleware.py", line 12, in call
web_1 | return self.process_response(request, response)
web_1 | File "/usr/local/lib/python3.9/site-packages/livesync/core/middleware.py", line 16, in process_response
web_1 | if settings.DEBUG and 'text/html' in response['Content-Type']:
web_1 | File "/usr/local/lib/python3.9/site-packages/django/http/response.py", line 144, in getitem
web_1 | return self._headers[header.lower()][1]
web_1 | KeyError: 'content-type'
web_1 | [26/Dec/2020 09:08:41] "GET /media/1.png HTTP/1.1" 500 70679