@ste74 the patch is applied in the wrong directory. The patch command is invoked inside the "src" directory, which creates 2 new directories ("icons" and "icons-dark"), which contain the missing files. You need to either move the created directories inside the "breath" directory or invoke patch with the -d option like so:
patch -d breath -Np1 -i ../0001-Fix-for-media-playback-status-and-Switch-display-ico.patch
This seems to fix the issue, the files are present in the package build using after this change to PKGBUILD.
EDIT: Better yet, maybe fix the error in the https://gitlab.manjaro.org/artwork/themes/breath/tree/master source repo