How can the IF or #IF work in the automation rule for sending emails?

Request: In the JSM automation rule for sending emails, the email body needs to display the value of a field from a form. If the field is empty, it should display "null"; otherwise, it should display the field value directly.

Below is a rule written using "if" or "#if", but the correct value is not displayed in the email body.

Could you tell me what's wrong? thanks.  Both methods should display "ssds", but currently the IF statement returns null, and the #if statement returns empty.

for if statement: {{if(issue.customfield_12345, issue.customfield_12345, "null")}}

for #if statement:

{{#if(issue.customfield_12345)}}

{{issue.customfield_12345}}

{{else}}

null

{{/}}