fix tests by setting publication date on datafile

Author: stevenwinship

src/test/java/edu/harvard/iq/dataverse/featured/DataverseFeaturedItemTest.java

@@ -36,6 +36,7 @@ public void test_validTypeAndDvObject() {
         assertEquals(ds, dfi.getDvObject());
 
         // update with Datafile
+        df.setPublicationDate(Timestamp.from(Instant.now()));
         dfi.setDvObject("Datafile", df);
         assertEquals("datafile", dfi.getType());
         assertEquals(df, dfi.getDvObject());

src/test/java/edu/harvard/iq/dataverse/util/json/JsonPrinterTest.java

@@ -455,6 +455,7 @@ public void testDataverseFeaturedItemDatasetTest() {
     public void testDataverseFeaturedItemDatafileTest() {
         Dataverse dataverse = createDataverse(42);
         DataFile dvObject = createDatafile(1L);
+        dvObject.setPublicationDate(Timestamp.from(Instant.now()));
 
         DataverseFeaturedItem fi = new DataverseFeaturedItem();
         fi.setDataverse(dataverse);