Currently, when expanding variables in the template, any empty values are removed along with the whole tag.

Apparently, there is a need to actually send empty values in some cases.

With this change, prepending the variable name with ~ will cause the empty value to be kept and appear in the resulting JSON.

Example:

Template:

{
    "name1": ${empty_value},
    "name2": ${~empty_value}
}

Where empty_value = "", will result in the following JSON:

{
    "name2": ""
}