Popup Maker: Fix WP User Frontend Invalid Post error

fix_wp_frontend_invalid_post_error.php

<?php

  /**
   * NOTE: Popup Maker 1.22.0 runs the template_redirect at priority 1 (before it was 10).
   *       This snippet's outer action priority runs at -1 now so it can still fix
   *       the Invalid Post error. If we left the original outer priority at 1, the
   *       original non-Popup Maker pid would never get put back into the URL for
   *       the redirect and we'd see the Invalid post error again.
   */

  add_action( 'template_redirect', function () {                                                                                                       
      if ( empty( $_GET['pid'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Recommended
          return;                                                                                                                                      
      }           
                                                                                                                                                       
      // Normalize array to scalar (e.g. ?pid[]=1 from some page builders).                                                                            
      if ( is_array( $_GET['pid'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Recommended
          $_GET['pid'] = reset( $_GET['pid'] ) ?: null; // phpcs:ignore WordPress.Security.NonceVerification.Recommended                               
          if ( empty( $_GET['pid'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Recommended                                              
              return;                                                                                                                                  
          }                                                                                                                                            
      }                                                                                                                                                
                  
      $popup_id = absint( $_GET['pid'] ); // phpcs:ignore WordPress.Security.NonceVerification.Recommended                                             
  
      // If pid doesn't point to an actual popup, temporarily remove it so Popup                                                                       
      // Maker (priority 0) doesn't redirect, then restore it at priority 11 so
      // other plugins (e.g. WP User Frontend) can still use it during rendering.                                                                      
      if ( $popup_id > 0 && 'popup' !== get_post_type( $popup_id ) ) {                                                                                 
          $saved_pid = $_GET['pid']; // phpcs:ignore WordPress.Security.NonceVerification.Recommended                                                  
          unset( $_GET['pid'] ); // phpcs:ignore WordPress.Security.NonceVerification.Recommended                                                      
                                                                                                                                                       
          add_action( 'template_redirect', function () use ( $saved_pid ) {
              $_GET['pid'] = $saved_pid; // phpcs:ignore WordPress.Security.NonceVerification.Recommended                                              
          }, 11 );                                                                                                                                     
      }
  }, -1 );