Templates now contain basic conditional tag support, here is an example:
{if:CUSTOMER_NAME} Hello {CUSTOMER_NAME}, <br> {else} Dear Customer, <br> {endif:CUSTOMER_NAME}
Or for the address:
{ADDRESS_LINE_1} <br/> {if:ADDRESS_LINE_2}{ADDRESS_LINE_2} <br/>{endif:ADDRESS_LINE_2} {ADDRESS_SUBURB} <br/>
Nested tags are not supported. Ensure the tag within {if:} and {endif:} match exactly for it to work.