ensure group_by_join_statement is nil when group_by_statement is nil

app/models/custom_field/order_statements.rb

@@ -67,19 +67,23 @@ def order_null_handling(asc)
   # which differ for multi-value select fields,
   # because in this case we do want the primary CV values
   def group_by_statement
-    return unless field_format.in?(%w[list date bool int float string link])
+    return unless can_be_used_for_grouping?
 
     order_statement
   end
 
   def group_by_join_statement
+    return unless can_be_used_for_grouping?
+
     return join_for_group_by_list_sql if field_format == "list"
 
     order_join_statement
   end
 
   private
 
+  def can_be_used_for_grouping? = field_format.in?(%w[list date bool int float string link])
+
   def join_for_order_sql(value:, join: nil, multi_value: false)
     <<-SQL.squish
       LEFT OUTER JOIN (