fix for mongoid 7

Author: scambra

CHANGELOG.rdoc

@@ -4,6 +4,7 @@
 - Support loading jquery-ui externally, without jquery-ui-rails gem and ask AS to load JS/CSS for addons based on jquery-ui
 - Support usage with importmap
 - Add reset_form to search and field_search, when enabled, reset link will clear input fields in the search form, instead of refreshing the list without search and closing the form.
+- Fix for mongoid 7
 
 = 3.7.2
 - Fix routes

lib/active_scaffold/finder.rb

@@ -618,7 +618,8 @@ def find_page(options = {})
       options[:page] ||= 1
 
       find_options = finder_options(options)
-      query = beginning_of_chain.where(nil) # where(nil) is needed because we need a relation
+      query = beginning_of_chain
+      query = query.where(nil) if active_scaffold_config.active_record? # where(nil) is needed because we need a relation
 
       # NOTE: we must use :include in the count query, because some conditions may reference other tables
       if options[:pagination] && options[:pagination] != :infinite