For certain requests, UPSRateRequest::getRates() can fail because the foreach ($ups_rates['RateResponse']['RatedShipment'] as $ups_rate) loop assumes that the $ups_rates['RateResponse']['RatedShipment'] is always a multidimensional array with each RatedShipment indexed under a number
0 = array
1 = array
2 = array
However, if there is only one RatedShipment then they are not indexed and instead the contents are directly inside the RatedShipment array. The foreach loop then splits them out and none of the expected array contents in $ups_rate are there causing a fatal php error.
Create a shipment with the following address
Canada
123 Fake St
Iqaluit, Nunavut X0A2H0
Active
4.0
Code
Fixed UPSSdk::getShipmentShopRates so it returns the expected array structure when there is only one rate.