Window to enter suggested category not shown because if(isset($form_values)) condition is not correctly evaluated

Hello,

The option Allow "Suggest a category" is activated.
The user can see the option but the window to enter the suggestion is not there.

After tracking the issue back to the code I found out that the condition isset($form_values) seems to return: false.
When I modify the code with: if (!isset($form_values)) i.e.

if (!isset($form_values)) {
    if ($form_values['category'] == 0) {
      $form['new_cat'] = array(
        '#title' => t('Suggested Category'),
        '#type' => 'textfield',
        '#weight' => -1,
        '#default_value' => null,
        '#description' => t('Please enter your suggested category for the question.'),
        );
    }
  }

the window is there and the suggest category function works correctly including assigning the new category to an expert and adding it as a term of the FAQ vocabulary

Am I breaking something else with this modification?

Alex