Error with sed when running fixElectronBug.sh on macOS

[ltfschoen]

When this Bash script (paritytech/fether/packages/fether-electron/scripts/fixElectronBug.sh) is run with the yarn electron command, I get error:

sed: -e expression #1, char 1: unknown command: `.'

It is because sed --version returns sed (GNU sed) 4.5, where GNU Sed does not appear to be supported, or because I am not using GNU Sed correctly.
This is because I installed GNU Sed with brew install --with-default-names gnu-sed, which allows the GNU Sed binary to be run with sed or /usr/local/bin/sed, whereas if I had installed GNU Sed with brew install gnu-sed it would only allow GNU Sed binary to be run with /usr/local/bin/gsed.