Ansible - User Input

If a user is prompted for some input and in this case they don't input anything and just press enter a " '' " value is passed into the variable:

Example of the question:

- name: "vs_rule"   
  prompt: "enter the associated rule [Press enter to skip or enter in the following format: rule1 rule2]"   
  private: no

I'd like to use something similar to the below code but I don't want to pass the quotes onto the LTM (''), since the user will see the following error upon running the debug to show them the output: (note: this error is coming from the LTM, not Ansible after ""tmsh -c ''"" is entered in bash):

 "std exception: (basic_string::substr), exiting..."

Is there a way to filter out the '' after the else and just send nothing to the LTM?

- "{{ 'tmsh list ltm rule ' + vs_rule + '' if vs_rule else '' |default([]) }}" 

Here are two other ways this has been tried with no success:

- "{{ ((vs_rule | trim()) == "") | ternary(' do nothing', 'tmsh list ltm rule ' + vs_rule) }}"

and by adding the default field to the vars_propmt:

- name: "vs_rule"
  prompt: "enter the associated rule [Press enter to skip or enter in the following format: rule1 rule2]"
  private: no
  default: ""