ml: Empty file name given to OpenCV

[sbarber2]

I see this on the console sometimes, not sure what I was doing to cause it:

OpenCV: Couldn't read movie file ""
[ERROR:[email protected]] global cap.cpp:166 open VIDEOIO(CV_IMAGES): raised OpenCV exception:

OpenCV(4.8.0) /Users/xperience/GHA-OpenCV-Python/_work/opencv-python/opencv-python/opencv/modules/videoio/src/cap_images.cpp:293: error: (-215:Assertion failed) !_filename.empty() in function 'open'