Be more verbose if there are no metadata found
Just notice this after running optipng -strip all -i 0 -o 9 mat2.png
for !20 (merged)
Before:
mat2 -s mat2.png
[+] Metadata for mat2.png:
SignificantBits: 8 8 8 8
PixelsPerUnitX: 15118
PixelsPerUnitY: 15118
PixelUnits: meters
Software: www.inkscape.org
Title: Adwaita Icon Template
Author: GNOME Design Team
Copyright: CC Attribution-ShareAlike http://creativecommons.org/licenses/by-sa/4.0/
After:
mat2 -s mat2.png
[+] Metadata for mat2.png:
Maybe output something along the lines of "No metadata found" instead of just nothing