filter null values when retrieving sort

src/main/java/coop/libriciel/ipcore/utils/RequestUtils.java

@@ -37,10 +37,7 @@ import reactor.core.publisher.Mono;
 
 import java.io.*;
 import java.time.Duration;
-import java.util.Calendar;
-import java.util.Date;
-import java.util.HashMap;
-import java.util.Optional;
+import java.util.*;
 import java.util.function.Function;
 import java.util.function.Supplier;
 import java.util.stream.Stream;
@@ -149,6 +146,7 @@ public class RequestUtils {
         return pageable.getSort().stream()
                 .map(Sort.Order::getProperty)
                 .map(prop -> EnumUtils.getEnum(enumClass, prop))
+                .filter(Objects::nonNull)
                 .findFirst()
                 .orElse(defaultValue);
     }