Change email xmpp header if it already exists

src/freedombone-addxmpp

 if [ -f /home/$USERNAME/.muttrc ]; then
     if ! grep -q "Jabber-ID" /home/$USERNAME/.muttrc; then
         echo "my_hdr Jabber-ID: $EMAIL_ADDRESS" >> /home/$USERNAME/.muttrc
+    else
+        sed -i "s|my_hdr Jabber-ID.*|my_hdr Jabber-ID: $EMAIL_ADDRESS|g" /home/$USERNAME/.muttrc
     fi
 fi