Allow uc_paypal_ec_form form to be used programatically

I needed to rearrange my cart page, which involved displaying the Paypal express button inside another cart pane rather than as its own pane. So I turned off the Paypal express pane and used drupal_get_form('uc_paypal_ec_form') in a theme function, but this did not work because uc_paypal_ec_form returns nothing if its expected cart pane is disabled.

It seems like that check is not necessary since the function should not be called in the first place if it was not intended to be displayed.