Fix MJPEG fallback when still image URL is missing with basic auth

I picked up an old DCS-930L (circa 2010) camera to test with
to fix #94877

homeassistant/components/mjpeg/camera.py

@@ -145,6 +145,7 @@ async def async_camera_image(
         try:
             async with asyncio.timeout(TIMEOUT):
                 response = await websession.get(self._still_image_url, auth=self._auth)
+
                 image = await response.read()
                 return image