fix failure in mlt with dates, this does mean that currently, mlt, when based on fetching the source and parsing it, does not do mlt on numbers

modules/elasticsearch/src/main/java/org/elasticsearch/action/mlt/TransportMoreLikeThisAction.java

@@ -151,6 +151,7 @@ public class TransportMoreLikeThisAction extends BaseAction<MoreLikeThisRequest,
                     boolBuilder.mustNot(termQuery(uidTerm.field(), uidTerm.text()));
                 } catch (Exception e) {
                     listener.onFailure(e);
+                    return;
                 }
 
                 String[] searchIndices = request.searchIndices();

modules/elasticsearch/src/main/java/org/elasticsearch/index/mapper/json/JsonDateFieldMapper.java

@@ -141,7 +141,11 @@ public class JsonDateFieldMapper extends JsonNumberFieldMapper<Long> {
     }
 
     @Override public String valueAsString(Fieldable field) {
-        return dateTimeFormatter.printer().print(value(field));
+        Long value = value(field);
+        if (value == null) {
+            return null;
+        }
+        return dateTimeFormatter.printer().print(value);
     }
 
     @Override public String indexedValue(String value) {