Update GTLRService.m
Update GTLRService.m

Fix static analysis warning for
`GTLRService.m:2479:30: Converting a pointer value of type 'NSNumber * _Nullable' to a primitive boolean value; instead, either compare the pointer to nil or call -boolValue`
google/google-api-objectivec-client-for-rest,google/google-api-objectivec-client-for-rest,google/google-api-objectivec-client-for-rest,google/google-api-objectivec-client-for-rest,google/google-api-objectivec-client-for-rest