Order List: convert wrong type (blank string) to correct type (empty array) for taxes

[mindgraffiti]

p99K0U-24e-p2

Incorrect type, blank string, occasionally returns from an API response. In the Order List Mapper, check for a blank string and convert it to an empty array.

[iamgabrielma]

Somewhat related to #1201, where we were only expecting Strings from a mixed-type endpoint, causing the data to not decode properly.