Better handling of errors on trial license request (#14886)

* Fix behavior on blank site url on trial requests

* Adding trial license error response handling

* Changing text based on PR review comments

app/license.go

@@ -218,6 +218,10 @@ func (s *Server) RequestTrialLicense(trialRequest *model.TrialLicenseRequest) *m
 	defer resp.Body.Close()
 	licenseResponse := model.MapFromJson(resp.Body)
 
+	if _, ok := licenseResponse["license"]; !ok {
+		return model.NewAppError("RequestTrialLicense", "api.license.request_trial_license.app_error", nil, licenseResponse["message"], http.StatusBadRequest)
+	}
+
 	if _, err := s.SaveLicense([]byte(licenseResponse["license"])); err != nil {
 		return err
 	}