Using `sed`:

    sed '/[0-9]/!s/ //g' filename

This would remove spaces on all lines that do not contain a digit.

Using `awk`:

    awk '!/[0-9]/{gsub(" ", "", $0)};1' filename


For removing the space only between the first two words (here using GNU `sed` for `-r`, use `-E` instead on BSDs):

    sed -r '/[0-9]/!s/([^ ]+) ([^ ]+)/\1\2/' filename