List of steps to reproduce (step by step, including full links if applicable):

• call a query like {{#cargo_query:|tables=my_table|fields=field1,field2,field3|format=template|template=my template}}
• the table my_table must contain rows with null values for certain fields (e.g. field2)

What happens?:

• the positional arguments shift when cargo internally calls my_template
• so if field2 contains a null value, the CargoTemplateFormat class returns {{my template|1=field1|2=field3}}

What should have happened instead?:
{{my template|1=field1|2=field2|3=field3}} is returned for that row or {{my template|1=field1|3=field3}} if field2 is empty

Software version (if not a Wikimedia wiki), browser information, screenshots, other information, etc.:
since cargo commit e1f47f73faa37d657b50799a867a2ecc33603fa1