java.lang.NullPointerException due to 'Map<String, Integer>' may not contain keys of type 'Path<String>'

Question

I am facing an issue in a springboot project, I am trying to retrieve statistics of "Tickets" that are handled ontime using jpa specifications. Ticket are given a number of days to handle based on the purpose.

Here is the error:

java.lang.NullPointerException: null
    at com.ticketcorp.ticket.repository.TicketSpecification.lambda$isOntime$c9c337fb$1(TicketSpecification.java:208) ~[classes/:na]

Which i Believe is to be expected since i got this warning on the same line:

'Map<String, Integer>' may not contain keys of type 'Path<String>' 

Here is my Ticket Entity:

@Table(name = "tickets")
public class Ticket {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    private String code;
    private String purpose;
    @Lob
    @Column(columnDefinition = "TEXT")
    private String content;
    @Lob
    @Column(columnDefinition = "TEXT")
    private String solution;
    @Lob
    @Column(columnDefinition = "TEXT")
    private String comment;
    private int status;
    private LocalDateTime createdAt= LocalDateTime.now();
    private LocalDateTime handledAt= LocalDateTime.now();
}

Here is my Ticket Specification:

    public class TicketSpecification {
    public static Specification<Ticket> isOntime(ArrayList<Purpose> purposes) {
           
       return (root, query, builder) -> {
        /*Example of content for nameAndDurationMap: {Suggestion=25, Bug report=1}*/
        Map<String, Integer> nameAndDurationMap = PurposeUtils.PurposeArrayToNameDurationMap(purposes);
                
                return builder.le(
                        builder.diff(
                                builder.function("unix_timestamp", Long.class, root.get(Ticket_.handledAt)),
                                builder.function("unix_timestamp", Long.class, root.get(Ticket_.createdAt))
                        )
                        , nameAndDurationMap.get(root.get(Ticket_.purpose)) * 86400);/*Line 208*/
    
            };
        }
    }

Here is my Ticket Service:

@Service
public class TicketService {
    @Autowired
    private TicketRepository ticketRepository;

public String countTicketsHandledOnTime(){
    int handledStatus=2;

    Specification<Ticket> allTicketHandledOnTimeQuery =where(TicketSpecification.isHandled(handledStatus)).and(TicketSpecification.isOntime(purposes));

return String.valueOf(ticketRepository.count(allTicketHandledOntimeQuery));
}

}

Here is Purpose POJO Model:

public class Purpose{
    private String id;
    private String name;
    private String description;
    private int level;
    private int duration;
}

Here is PurposeUtils : It takes a list of purposes and generate a hashmap of purpose and number of days it should take to handle a ticket of that purpose.

public class PurposeUtils {
    public static Map<String, Integer> PurposeArrayToNameDurationMap(ArrayList<Purpose> purposes) {
        Map<String, Integer> purposeMap = new HashMap<String, Integer>();
        for(Purpose purpose: purposes) {
            purposeMap.put(purpose.getName(), purpose.getDuration());
        }
        return purposeMap;
    }
}