apngasm: apngasm --output file fails if its path contains a relative link pointing to the upper directory (two dots unix style)

My intent in human words:

• Change to the directory holding your animation files.
• Take all PNG files from this current directory and then
• create an animation output file in the directory above

And in command line syntax this is:

➜  ~ cd ~/Documents/Feedback/animation
➜  apngasm  *.png -o ../anim1.png -d 3000
./01.png => Delay=(3000/1000) sec
./02.png => Delay=(3000/1000) sec
./03.png => Delay=(3000/1000) sec
3 Frames
libc++abi.dylib: terminating with uncaught exception of type boost::filesystem::filesystem_error: boost::filesystem::create_directories: Invalid argument
[1]    12405 abort      apngasm *.png -o ../anim1.png -d 3000

This seems to be valid syntax to me according to the manpage.

• But somehow apngasm seems to choke on it.
• APNG Assembler v3.1.6 on macOS 11.2.1 Big Sur

Note: I also detected #78 maybe the two are related and have an underlying bug of macOS Big Sur together? Though #78 fails way later, actually it thinks it is successful (no errors or complaints) but creates no output file at all.