Write SOSL Queries error. The class works and returns data however, i get this error when trying to check: There was an unexpected error in your org which is preventing this assessment check from completing: System.ListException: List index out of bounds

Hi brandom,

 Is very important to add 

RETURNING Contact(LastName),Lead(Name)

Try this

public class ContactAndLeadSearch {
    public static List<List<sObject>> searchContactsAndLeads(String p1){
        try {
                       List<List<sObject>>cssosl = new List<List<sObject>>([FIND :p1 IN ALL FIELDS RETURNING Contact(LastName),Lead(Name)]);
                       System.debug('in try' + cssosl);
                       return cssosl;
                   } catch (ListException e) {
                       System.debug('fail: '+ e.getCause());
                       return null;
                   }    
    }
}