DATACMNS-1581 - Tighten nullability constraints for Sort parameters in PageRequest factory methods.

We now explicitly rejects null values for the Sort parameters in the constructor of PageRequest to avoid the creation of invalid instances if the IDE validation of nullability constraints is not in use.

src/test/java/org/springframework/data/querydsl/QPageRequestUnitTests.java

@@ -51,4 +51,11 @@ public class QPageRequestUnitTests extends AbstractPageRequestUnitTests {
 
 		assertThat(pageRequest.getSort()).isEqualTo(QSort.by(user.firstname.asc()));
 	}
+
+	@Test // DATACMNS-1581
+	public void rejectsNullSort() {
+
+		assertThatExceptionOfType(IllegalArgumentException.class) //
+				.isThrownBy(() -> new QPageRequest(0, 10, (QSort) null));
+	}
 }