#101 - Do not activate custom-search classes on all page-views

_Overview_: Civi 5.41 began migrating the "custom search" layer to an extension
(`legacycustomsearches`).  `dataprocessor` uses the "custom search" layer in a way that
provokes a hard/ubiquitous error during upgrade.  This revision makes it more robust
against upgrade errors.

_Before_: `hook_config` unconditionally (*on all page-views*) loads
`CRM_DataprocessorSearch_Form_Search_Custom_DataprocessorSmartGroupIntegration` and calls
`redirectCustomSearchToDataProcessorSearch()`.

_After_: `hook_config` only calls `CRM_DataprocessorSearch_Form_Search_Custom_DataprocessorSmartGroupIntegration`
if it's needed.

_Comments_:

* The error arises from when autoloading the base-class `CRM_Contact_Form_Search_Custom_Base`. This class
  exists, but it won't be available until the upgrade is complete.
* Strictly speaking, the two conditionals (on `$currentUrl` and `ssID`) are sufficient. I threw in a
  third conditional (`class_exists()`) as an extra bit of paranoia.
* I did a light `r-run` to ensure that the upgrade process works with the patch. However, I did not
  test the redirect.
* We're planning to include a short-term work-around in 5.41.1. However, this work-around will go away
  soon (eg 5.42 or 5.43).

CRM/DataprocessorSearch/Form/Search/Custom/DataprocessorSmartGroupIntegration.php

@@ -100,16 +100,14 @@ class CRM_DataprocessorSearch_Form_Search_Custom_DataprocessorSmartGroupIntegrat
    * check whether we are calling saved data processor search and if so
    * redirect it to the right url. As the custom search will fail.
    *
-   * @param $currentUrl
+   * @param int $ssID
+   *   Saved Search ID
    * @throws \CRM_Core_Exception
    */
-  public static function redirectCustomSearchToDataProcessorSearch($currentUrl) {
-    if (stripos($currentUrl, 'civicrm/contact/search/custom')===false || !CRM_Utils_Request::retrieve('ssID', 'Integer')) {
-      return;
-    }
+  public static function redirectCustomSearchToDataProcessorSearch($ssID) {
     // Load saved search to check whether this is a data processor search.
     $savedSearchDao = new CRM_Contact_DAO_SavedSearch();
-    $savedSearchDao->id = CRM_Utils_Request::retrieve('ssID', 'Integer');
+    $savedSearchDao->id = $ssID;
     if (!$savedSearchDao->find(TRUE) || empty($savedSearchDao->form_values)) {
       return;
     }

dataprocessor.php

@@ -164,7 +164,14 @@ function dataprocessor_civicrm_tabset($tabsetName, &$tabs, $context) {
  */
 function dataprocessor_civicrm_config(&$config) {
   _dataprocessor_civix_civicrm_config($config);
-  CRM_DataprocessorSearch_Form_Search_Custom_DataprocessorSmartGroupIntegration::redirectCustomSearchToDataProcessorSearch(CRM_Utils_System::currentPath());
+
+  $currentUrl = CRM_Utils_System::currentPath();
+  if (stripos($currentUrl, 'civicrm/contact/search/custom') !== FALSE && CRM_Utils_Request::retrieve('ssID', 'Integer')
+    && class_exists('CRM_Contact_Form_Search_Custom_Base')) {
+    // NOTE: Do not load this class unless we're very likely to need it.
+    CRM_DataprocessorSearch_Form_Search_Custom_DataprocessorSmartGroupIntegration::redirectCustomSearchToDataProcessorSearch(
+      CRM_Utils_Request::retrieve('ssID', 'Integer'));
+  }
 }
 
 /**