chore(i18n): fix parser for currency patterns without fraction digits

Previously, it was assumed that all currency pattern would have fraction digits.
However, in [closure-library@b9155d5][1] the `agq_CM` locale was modified to
have such a pattern (namely `#,##0\u00A4`).
This commit modifies the parser implementation to account for pattern without a
decimal point (and thus no fraction digits).

[1]: https://github.com/google/closure-library/commit/b9155d5966a228cb33f367c30c275c833b30e3ff#diff-02793124214ad0470ccea6f86b90d786R711