Error in mw -a for email addresses starting with letter "i" due to overbroad regex

[IzaacMammadov]

This error only comes up if you have an email address starting with the letter "i" and then attempt to add another email address.
/usr/bin/mw: line 229: [: zaac@mammadov.co.uk": integer expression expected

where my email address is izaac@mammadov.co.uk

The offending regex in question is on line 227: for x in $(sed -n "/^macro.* i[0-9] / s/\(^macro.* i\| .*\)//gp " "$muttrc" | sort -u; echo 0); do

It's designed to match the i1/i2/i3 in the .muttrc file, but instead matches the space and start of my email address.